infancy

Perceiving the structure of the visual environment involves two core elements:

 local and global form processing

• Global visual processing is typically rapid and automatic; linking local features of a scene together, spatial relationships

• Local processing is slower; involves selective attention to individual elements of a scene

• By age 5 global typically precedes local perception

Kanizsa illusory contours

• Global processing is required to induce illusory form

• Allow for evaluation of both global and local perception

• Illusion is built on the assumption that the circles must be complete (the square is placed on top of the circles)

  • Motion supports this because if they move together they must be whole

age for development of moving vs static figures

• 3-4 months infants are able to see moving illusory contours

• 7-8 months infants are able to see static illusory contours

What causes the shift from not perceiving contours to perceiving them at 7 months old?

• infants less than 6 months of age have only a weak ability to perceive illusory contours.

• These studies suggest that motion information promotes infants perception - @4 months infants can differentiate when puzzle is moving

• Hence, the neurophysiological filling-in mechanisms, which underlie illusory shape formation must be operating by 4 months of age.

• Global processing matures around 7 months old

Why does the brain create illusory shapes in the first place? What underlying systems are involved?

• Subjective surfaces are characterized by two properties. First, they appear to be brighter than the surrounding area, although there is no corresponding physical luminance difference (illusory brightness). Second, a sharp border is perceived surrounding the area of brightness enhancement (illusory contour).

• Subjective contours: capability of encoding physically unconnected parts as belonging to a single surface; that is, of filling the gaps between the inducing elements of the Kanizsa figure in order to discern illusory contour.

• Organizing fragments of input/filling in blanks

• Helps us recognize objects quickly and separate things from the background

• Switch from local to global processing

Haptic-visual switch

occurs around 4-5 months

Transfer of info between haptic and visual systems

Info can be transferred from haptic processing to visual around 2 months

Info can be transferred from visual to haptic around 5 months - effect cannot be reversed

• Visual system matures to block some processing by haptic system because instrumental function temporarily interferes with the perceptive function of the hand

  • So strongly driven at this age by visual processing that there is no opportunity to explore in the opposite direction (can explore via vision at this age instead of grabbing things first whereas previously they could only explore via grabbing bc visual processing was not mature)

Why does haptic perception develop first

• Visual perception develops later because you have to learn how to interpret it

  • Ex learning that something smaller is likely farther away

• Haptic perception develops sooner because it is direct

ASD group seems to perceive a square less often than the TD group on eye tracking

• Reaction time measure, accuracy measure, eye tracking measure

  • Accuracy - they had to choose what shape they were seeing previously (if they chose the square then they were seeing the illusion completely)

    • Identical in ASD and TD

  • Reaction time

    • Equally fast unless you add distractors

  • Eye tracking

    • ASD group looked less at the center of the illusion than TD children

      • Center requires global processing - looking at the center implies that you recognize something is there = illusion is working

      • Local processing would be more likely to look at individual aspects of illusion (pacmen)

How does the perceptual system of autistic children differ, and what does it mean when it is described as “impaired”?

• Detail-oriented processing style in ASD

• Reduced global processing

• Both groups had positive global processing-LP differences, but TDC had larger positive global processing-LP values than ASD

• Across both conditions, there was a significant large main effect of group for looking behaviors such that global processing-LP difference was smaller for individuals with ASD compared to TDC

• Results suggest a delayed developmental trajectory in visual processing. 

  • Delay in global processing development rather than impaired

• ASD group seems to perceive a square less often than the TD group on eye tracking

Methods for Autism pattern processing paper

• participants: typically developing and autistic 7-13 yo’s

• KIC task and eye tracking

  • eye tracking and touch location

  • Participants were required to select KICs that matched a previously presented real (nonillusory) sample shape.

  • On each trial, one

    of five sample real shapes (square, diamond, rectangle,

    triangle, or trapezoid) appeared for 1 sec at the center

    of the screen, followed by a black screen for 1 sec, and

    then two simultaneously presented KIC figures of the

    same size; one induced the appearance of the sampleorm, which we refer to as the target KIC (correct

    match), the other was a distractor KIC.

  • The experimental paradigm consisted of two condi-

    tions presented in a fixed order: the first assessed basic

    KIC recognition; the second assessed KIC recognition in

    the presence of “noise,” which consisted of randomly

    arrayed pacman elements, thus creating local interfer-

    ence

• Measured accuracy (touching correct stimulus) and reaction time (eye tracking)

KIC

KICs are comprised of strategically

placed “pacman” elements that induce the perception

of a shape or contours in the absence of physical

boundaries

Childhood Disintegrative Disorder 

• Apparent normal development up to the age of at least 2 years, which is followed by a definite loss of previously acquired skills.

• behaviour modification and special education to help encourage the reacquisition of basic adaptive skills can be applied

CDD vs ASD

• differs from classical autism in the mode of presentation, both in terms of the prolonged period of normal development (regression occurs after 2 years) and the very marked loss of skills associated with the condition.

  • However, among children with classical autism approximately 30% develop normally or near normally during the first year or two of life before developmental skills regress (autistic regression - prior to 2 years)

• Outcome findings indicate that development after regression is less satisfactory in patients with CDD than classical autism or other types of childhood pervasive development disorder

• It was seen that CDD individuals tended to have lower functioning, were more aloof, and had a greater incidence of comorbid epilepsy than kids with autism

Low birth weight

• the majority of VLBW children also experienced poorer growth attainment

• mainly hyperactivity and attentional weaknesses, but also shyness and withdrawn behavior, difficulty in social skills, and anxiety and depression.

• Subjects who grow rapidly and demonstrate catch-up growth are considered at greatest risk for the medical complications

• CP, vision loss, hearing loss

• Sensory impairment

• Lower IQ and lower academic achievement, less high school/college diploma

• There were no differences between the VLBW and NBW subjects on the CHIP-AE, a measure of health status in satisfaction with health, self-esteem, physical and emotional discomfort, and physical limitations.

• VLBW females later demonstrated greater catch-up growth than VLBW males

• less risk-taking, including drug and alcohol abuse and sexual activity among VLBW subjects

extra card

extra card

What are the differences between optimal, critical and sensitive periods?

• Optimal: (a) both the onset (opening) and offset (closing) of openness to experience is variable rather than absolute and (b) phonological acquisition involves the emergence of a series of nested capabilities, each with its own sensitive period and each best explained at one of several different levels of specificity

  • biologically (and experientially) determined period, usually early in ontogeny, during which some aspect of an organism’s neural and behavioral functioning is especially sensitive to a particular environmental factor. 

• Critical: it proposes that there is a biologically determined, specific and ‘‘fixed’’ or invariant period of time during development during which an organism’s neural functioning (and related behavioral competence) is open to effects of external experiential input.

• Sensitive: the periods during which biobehavioral systems can be altered by experience that are  more variable than surmised in the classic conception of a ‘‘critical period,’’

Age of acquisition of a second language relates to proficiency

more overlap in the brain regions activated to first and second language in bilinguals who acquired their second language in early childhood than in individuals who acquired their second language after puberty

exposure to a language in infancy

• can have a lasting impact on level of attainment and neural organization for signed and spoken languages

  • ASL as a first language learned in infancy for deaf individuals activates visual cortex AND classic language areas in the left temporal lobe

Decline in nonnative speech perception is one of reorganization rather than loss

ERP to the nonnative contrast may be slower and/or be over different recording sites than is the ERP to native phonetic distinctions

Cochlear implant studies

• if children are implanted before age 3 1/2, the latency of a particular ERP component (P1) to sound becomes normal within 6 to 8 months following implantation; however, if they are implanted after this age, the outcome is more variable, and there is uniformly poor outcome in children implanted after 7 years of age.

  • Thus, the OP for speech-sound discrimination seems to have remained open with 0 input

Group differences at birth in ERP-components are significantly associated with later language development

• Poorer receptive language skills at 2.5 years

• Poorer verbal memory skills at 5 years

 expressive and receptive language performance at 10 months

•  substantially associated with cognitive and educational functioning 10 years later.

  • Better early language (10 months - REEL) abilities are related to better cognitive and academic performance at 11 years.

  • The receptive language scale is significantly associated with spelling, sentence repetition, the school functioning score and grade in German. 

  • Recommendations for the highest levels of schooling for boys and girls is significantly related to both language variables

adoption studies

• Korean children who were adopted into french families between the ages of 4-9 did not perform better than native french speakers (and performed worse than korean speakers) in their ability to discriminate korean consonant contrasts in adulthood

• FMRI studies show similar responses to French speakers in that the adoptees show activation in specialized language areas in the left hemisphere only to french with korean activating the same general auditory analysis areas as other foreign languages

• argues early experience does not have a lasting effect

RAP and language outcomes

• RAP efficiency evaluated with behavioral measures (operant-conditioned head-turn and habituation/recognition paradigms) differs as a function of family history and is predictive of later language outcome at 16, 24 and 36 months

• RAP threshold and being male together predicted 39–41% of the variance in 36-month language outcome

• Differences in individual RAP thresholds in infancy were not only strongly related to later language development, but were found to be the single best predictor of expressive and receptive language outcome at all subsequent ages

phonetic categories

the abstract speech sounds that a language uses to distinguish meaning

phonological categories

the abstract groupings of speech sounds in a language, defined by shared features like place and manner of articulation, voicing, and other patterns

• grammar

• syllable structure, substitution, and assimilation

lexical-semantic items

units of language that convey meaning, encompassing words, sub-word units like affixes, and multi-word expressions like idioms

how does phonological acquisition typically develop?

• acoustic abilities and the necessary underlying cortical substrates are in place from a very early age

• ability to perform fine-grained acoustic analyses in the tens of millisecond range appears to be critical to the decoding of the speech stream and the subsequent establishment of phonemic maps

• ability to efficiently and accurately process sequential rapidly presented, brief, auditory stimuli is fundamental

• Phonetic perception appears to involve specialized networks in the left temporal lobe in both adults and infants. 

• In our early research, we confirmed that listening experience (or the lack of such) is necessary to maintain sensitivity to a speech contrast by comparing infants and adults on their ability to discriminate native and nonnative phonetic contrasts

  • First year of life

• Several studies point to the possibility that under normal listening conditions, the offset of the OP for phonetic perception occurs sometime between 4 and 8 years of age.

• Preference to listen to speech over complex sounds, preference for good syllable form, categorical discrimination of content vs function words starting from birth impose direction and facilitation of subsequent perceptual learning of linguistic information

• During the first year of life, infants also tune perceptually to the phonotactic properties of the native language, and by 9 to 10 months show a preference for listening to acceptable and common sequences of phones

  • Perceptual narrowing

• during the first year of life infants tune to the consonant and vowel categories of the native language

• By the middle of the second year of life, infants use their native phonetic categories to represent words and guide word learning.

• These language-specific phonetic categories will subsequently be the phonological categories that guide rhyming and alliteration in the preschool years and that are essential for mapping the sounds of language onto the orthography when learning to read, write, and spell 

• Evidence for cascading OPs includes ear infection data

  • More ear infections in infancy (fluid disrupting sound transmission/experiential input) = less sharp phonetic categories in childhood

Benasich language learning experiment methods

Participants: control infants and infants born to families with a history of language learning impairments

• tested at 6,12, 24 and 36 months

Tones (frequencies of 100 or 300 Hz)  presented as pairs with varying interstimulus intervals of 300 and 70 ms

• presented as a passive oddball paradigm using a blocked design; the 70 ms ISI stimuli are presented first followed by a second block of 300 ms ISI stimuli

EEG signals are recorded; ERPs recorded

• Latencies and amplitudes were calculated 

• P150, N250, MMR

Language and cognitive scales

Benasich language learning experiment results

• In both the FH+ and FH− groups the 300 ms ISI stimuli elicited a biphasic responses to the first tone in the tone pair identified as the P150 and the N250 

  • no group difference

• Wave-forms of the ERP’s to the 70 ms ISI stimuli were significantly different from those to 300 ms ISI.

• For the 70 ms ISI control (FH−) group had significantly faster

  N250 responses as compared to FH+ infants

• right hemispheric N250 responses for FH+ infants appeared significantly later in time compared to the response in the left hemispheric. No such laterality effect was observed for FH- infants

•  no group differences in either the latency or the amplitude of the MMR response

• The amplitude of the MMR for the 70 ms ISI block significantly differed between the FH+ and FH−

• 70 ms ISI condition, FH+ infants show reduced positivity at frontal, frontocentral and central channels as well as a significantly smaller MMR (reduced positivity) in the left hemisphere as compared to the FH− infants.

• FH+ group scored significantly lower on the expressive language subscale of the PLS-3 compared to infants from the control group.

• infants with faster and more negative N250 waveforms scored higher on standardized measures of both expressive and receptive language

spatial cueing

• Investigates covert orienting

• Participants are  instructed to fixate on a marker at the center of the screen and to respond to the onset of a target stimulus that can appear to the left or right of the fixation marker by making a speeded keypress response. 

  • Onset of target is preceded by a cue that elicits a shift of attention to either the left or right

• Reaction time and accuracy are measured

  • Faster RT and better accuracy to the previously cued location = attention shifts to that location

Basic peripheral cueing paradigm

• two empty placeholder boxes are arranged to the left and right of the central fixation marker. The outline of one of the peripheral boxes is briefly brightened before a target appears randomly in either box after variable cue–target stimulus-onset asynchronies (SOAs). As soon as the target is detected, the participant responds by pressing a key

  • Increased brightness of peripheral box causes attention shift - reaction times are faster when cueing occurs on the same side that the target appears

• This orienting is automatic and reflexive (cannot be suppressed)

• If a target occurs in close temporal proximity to a peripheral event, facilitation dominates at the cued location resulting in speeded detection of the target. Once attention is drawn to new locations, inhibition becomes evident at the previously cued location, ex- pressed in elevated RTs.

Central cueing paradigm

• Orienting in response to centrally presented symbolic cues appears to be under voluntary (top down) control

• Do not directly indicate a spatial location, cues require interpretation

Dyadic interactions

person-person

• In the early months, infants primarily engage in dyadic, face-to-face interactions. 

• Reciprocation of emotions and affect between social partners

• with only six weeks of interactive experience, infants show a classic still-face effect

• by 3 months, infants have the skills to understand the relevance of the social signals necessary for learning and communication

triadic interactions

person-object-person

• involve two people in relation to some third external object, situation or event.

• essential for the development of abilities such as language and imitation

  • Ex learning names of novel object

dyadic/triadic development timing

Dyadic interactions

• infants are sensitive from birth onwards

• infants can initiate from 3 months onwards

Triadic interactions

• infants are sensitive from 3 months onwards

• infants can initiate from 6 months onwards

Gaze and social development

role in language development (eye gaze data correlates to vocabulary at 18 mo), babies need to learn words for individual objects first (through triadic interactions); eye gaze supports the development of theory of mind

How does ASD relate to joint attention and social cognition?

• Joint attention relates to the development of theory of mind 

  • Hidden toy in cup example with verbal vs visual instructions 3-5 year olds

• Shifts of attention are more often made between two (nonsocial) objects rather than between people

• children with autism tend not to use gaze cues in inferring the meaning of a novel word, which could play a role in the sometimes profound language deficits prevalent in this population

• Children with autism lack the differing EEG patterns between direct and averted eye contact

  • Lower grey matter density in STS - responsible for gaze processing

• Joint attention is impaired in ASD

  • Better joint attention is associated with larger vocabularies and few social and communicative difficultie

ASD and gaze-cueing

• it is possible that although the low-level perceptual aspects of gaze cueing (e.g., motion, luminance contrast, and geometry of sclera and pupil) are intact in children with autism, it is the higher level social cognition skills (e.g., attribution of emotional states) or their interactions with those basic processes that are impaired; in other words, the flexibility with which normally developing children use gaze cues is lacking in autism.

• They found that it was only the children with autism and a low mental age who failed to use gaze direction to shift their own attention.

• children with autism at age 2 years ) and with high-functioning autism at age 10 years appear to show cueing effects with moving eyes that are similar to those of normally developing children.

  • Effect found to not be a result of low level (motion processing)

• Children with autism respond to gaze cues differentially

  • Whereby typically developing children showed differences in cueing between counterpredictive gaze and arrow cues, whereas children with autism exhibited the same effects for both types of cues.

  • neither action observation nor observation of gaze direction influenced the performance of reach of children with autism. (differences in gaze integration to motor system)

• Stronger gaze-cueing effects are shown in the studies with younger children with autism.

  • Could be due to a development of voluntary control over joint attention in autism, whereas normally developed adults retain a more reflexive cueing response

results of studies that contradict previous conclusions of triadic interactions appearing at 9 months

• even four-month-old infants are attuned to the eye gaze of others and use eye gaze cueing in processing objects - sensitivity and functionality of triadic interactions

  • Watched video of adults gazing at an object, then gazed at the uncued object for longer indicating it was more novel and that the infant followed the gaze of the adult and acquired info about the object

  • Greater ERP responses to uncued objects in a similar paradigm - cued object was more familiar and previously processed

• three months of age, infants discriminated among various triadic interactions

  • Controversial whether this is functional

• 9 month ERP paradigm

  • joint attention context, the adult gazed at the infant’s face and then to a novel object that was displayed on a computer screen for 1 second. 

  • nonjoint attention context, the adult gazed only at the novel object.

  • The electrical brain activity of the infants was then measured as they viewed the novel objects presented on the computer screen

  • enhanced in amplitude (red line) when infants were engaged in a joint attention interaction compared with a nonjoint attention interaction

    • Processed objects differently depending on context

Modified Posner’s Gaze Cueing Paradigm

• Participants view a face stimulus at the center of the display. The gaze direction of that face substitutes the peripheral onset or symbolic arrow cues used in previous studies of attention orienting.

• Participants were asked to respond to target letters that appeared to either the left or the right of a schematic face with varying SOAs after the pupils of the face appeared, constituting a directional gaze cue.

• The response required was either the mere detection of the target’s appearance or the indication of its location or its identity by pressing appropriate response keys.

  • In infants track the saccades from target appearance to when they look at the correct location - calculate back to when the saccade began

• On valid trials, the target appeared in the gazed-at location, whereas on invalid trials, it occurred in the opposite location. 

  • Spatially uninformative cue

• RT was facilitated on valid-cue trials relative to neutral and invalid-cue trials, independent of response type. 

• another’s gaze shift results in a corresponding shift of attention in the observer, which has been labeled reflexive and therefore likened to orienting in response to peripheral cues

9 month old Senju differs from typical gaze cueing

differed from typical gaze cueing because the object appears first and then the face with the etes moves; looking time is measured - similar to the violation of expectation paradigm

evaluates if infants are interested in gaze because of low level processing (motion - they would be interested in any movement not just eyes) or are they interested in gaze because they understand (are driven to understand) that the eyes are a particularly useful/interesting cue and are socially relevant

Senju Experiment 1

• infants were familiarized (2 trials) with a face that shifted gaze to the right and left. Then infants were exposed to a loop stimulus (4 test trials) of objects (fish) either appearing to the right or left. Looking time was measured to evaluate reactions to incongruent gaze trials and congruent trials

  • infants looked significantly longer to congruent than to incongruent trials 

    • infants at this age are sensitive to eye–object relations.

    • preference for the potentially informative situation

Senju Experiment 2

•  Infants were shown a similar gaze paradigm, but the pupils remained static while the face translated laterally, so the gaze was the opposite direction of the motion (evaluating whether infants are sensitive to following gaze or following motion)

  • Infants looked significantly longer to the gaze-congruent trials than gaze-incongruent trials during the test phase

    • gaze direction, and not spatial congruency between motion and object location, contributed to the eye–object congruency effect found in Experiment 1

Senju Experiment 3

• Infants were shown displays involving a face and peripheral objects as in Experiment 1. However, in Experiment 3 the eyes were closed for a period of time before they opened already directed toward or away from the object. (evaluating if preceding eye contact is necessary for detection of gaze-object relations)

  • eye–object congruency did not have an effect on infants’ looking time in the test trials

    • a preceding period of direct gaze (i.e., perceived eye contact), plays a crucial role in the detection of eye–object congruency in 9-month-old infants

Senju Experiment 4

•  same as 3 but the opening of the eyes was accompanied by a lateral face motion in the same direction as the resulting eye gaze (evaluates if loss of congruency effect is due to no preceding eye contact or no lateral motion)

  • eye–object congruency did not have an effect on infants’ looking time during the test trials 

    • These results rule out the possibility that lateral motion that results in an averted gaze direction is a sufficient cue for 9-months-old infants’ sensitivity to gaze–object relations

    •  preceding period of direct gaze (i.e., a perceived eye contact) plays a crucial role in the detection of eye–object congruency in 9-month-old infants

Describe electrophysiological gamma-band responses

• 40Hz (20-60 measured in infants)

• Associated with maintaining an object in mind in adults

• Measured in right temporal areas

• Enhancement of gamma band activity in the unexpected disappearance condition

• Reduced in the expected disappearance condition

• Increased when train is hidden under tunnel (object in mind)

difference between vision data and EEG data

• EEG data is more sensitive

  • 1 value per condition in looking time data, EEG has many values/data points per condition

• Eye data is measuring the result of the processing rather than EEG measures the processing

Piaget’s view of object permanence compared to current view

• Piaget argued that infants under 8 months cannot represent hidden objects (no object permanence)

  • Currently evidence for infants as young as 4.5 months old succeeding with OP

• Piaget argued that at 4-8 months a child will search for a partially hidden object, at 8-12 months they will search for a hidden object in its first location even if they saw it be moved, 12-18 months they will search for the object in the right place only if they saw it be hidden, and by 18-24 months object permanence is fully developed

  • Current evidence argues he is wrong about the ages because failure to search does not equate to a lack of object permanence

  • 3,5 month old infants stare longer at impossible carrot event than possible carrot event - suggests they were aware the tall carrot existed even when it was hidden behind the screen

• Piaget argued mental symbolic representations don’t fully develop until 2

  • Children as young as 5mo have basic understanding of some number concepts (doll and screen math experiment) 

 continuity principle

• Objects exist and move continuously in space and time and retain their physical properties as they do so

  • Variable information becomes subject to an infant’s continuity principle allowing them to detect a continuity violation: this object is too tall to be hidden inside a short container

• Infants as young as 2.5-3 mo can detect basic continuity violations in occlusion, containment, and covering events

Variable continuity violations

infants fail to detect any continuity violation that involves a variable that they have not yet identified as relevant to an event category and hence do not yet include in visual representations of events from the category

Variables and their timing of development

• Variables develop at different times depending on the context

  • Height, width, transparency, color

  • 2.5 mo - behind/not behind

  • 3 mo - lowerage

  • 3.5-4 height/width

  • 9.5 transparency

  • 7 mo height/width in containment

Violation of expectation experiment

• Familiarization trials (5) a short box was hidden behind the screen; Infants watch test trials (2x3) of a tall cylinder moving behind a short screen; thick box condition = box filling space between screen and apparatus wall; thin box condition = space between screen and apparatus wall

  • if the infants (1) remembered the thick or thin box behind the screen, and (2) realized that the cylinder could pass behind the screen when the thin but not the thick box was present, then they should be surprised when this last expectation was violated.

  • Looking time was measured

• results suggest that the infants (1) remembered the thick or thin box behind the screen through the 3- or 4-min delay as well as the test trials, (2) realized that the cylinder could pass behind the screen when the thin but not the thick box was present, and (3) were surprised when this last expectation was violated

  • Results suggest that they represented the hidden box and used this representation to predict what would happen when the cylinder moved behind the screen.

Kaufman representation of occluded objects (carrot) experiment 1 methods

Experiment 1: digital sequences of real objects in (un)expected events to confirm experimental stimuli are realistic enough

• 6 month olds

• Each infant was shown sequences of video-recorded and digitally edited events depicting an object (a train engine) appearing, or failing to appear, out of a tunnel when it should or should not have been there

• familiarization trial

• four test events (expected appearance, unexpected appearance, expected disappearance, unexpected disappearance) were then presented in counterbalanced order

• Looking time was measured from the point at which infants began to look continuously from the start to the end of the event sequence. The event was repeated until infants looked away from the video monitor for 2 s.

Kaufman Experiment 1 results

• t-tests revealed a significant expected–unexpected looking time difference only within the disappearance condition

• infants are highly sensitive to the unexpected disappearance of an object (consistent with object permanence) but are less sensitive to an unexpected appearance

• reacted to computerized stimuli as if they were real objects

Kaufman Experiment 2 Methods

measured EEG of infants who were watching the disappearance events that we used in experiment 1

• 6 month olds

• infants viewed versions of the expected and unexpected disappearance films shown in experiment 1 - engine moved twice as fast

• EEG and looking times were recorded

  • Induced gamma-band activation was analysed comparing the two conditions during the part where the tunnel was lifted

Kaufman Experiment 2 Results

• gamma power was reduced in the expected disappearance condition.

• After the tunnel was lifted, there was significant enhancement of gamma-band activity in the unexpected disappearance condition relative to the baseline.

• results demonstrate a sustained period during which gamma power over the right temporal region was consistently higher while the object was occluded

• From this standpoint, object permanence is the ability to maintain a sufficiently strong representation of the object, despite competing evidence from visual input 

Kaufman Experiment 3 Methods

If the sustained gamma activity seen in experiment 2 is related to the representation of non-visible objects, it should also be evident in an ordinary event of temporary hiding, such as the expected appearance event in experiment 1

• watched expected and unexpected appearances in which a train was always revealed when the tunnel was lifted 

• EEG is measured

Kaufman Experiment 3 Results

• increased gamma power was evident at right temporal channels during the time and condition where the train should be hidden underneath the tunnel

• no increase in gamma activity in response to unexpected appearance

• no significant differences in gamma power either between the two conditions or from the baseline

• supports the notion that the increase in gamma power following the lifting of the tunnel in the first EEG experiment is related to representing an object in the face of contradictory visual input.

Carrot Study

3.5 month olds

• watched tall/short carrot move behind a tall occluder on a screen

  • got used to it disappearing

• part of the occluder was removed, so that you would be able to see the tall but not the short carrot as it moved along

• infants were surprised (looked longer) when the tall carrot unexpectedly disappeared behind the occluder

• continuity violation; object in mind

Face module

•  genetically programmed cortical model dedicated to faces

  • Fusiform face area: specific activation of a ventral temporal lobe area in response to faces

    • Involved in the initial encoding of faces

  • Existence of face responsive cells in infant monkeys as young as 6 weeks

    • Magnitude of a cell’s responses are at least 2 times larger when looking at faces than nonface objects

  • Newborn infants responding preferentially to faces

Two-process model

• no innate cortical model dedicated to faces

  • 1st process: Infants orient towards faces due to subcortical circuits

    • Orienting towards faces present in the temporal but not nasal visual hemifield = response is mediated by retinotectal pathway (subcortical)

    • After 6 weeks -emergence of cortical patterns for face processing

    • conspec

  • 2nd process: Conlern = activity dependent specialization of cortical circuits in response to face inputs

How does face processing develop throughout the lifespan?

• Ability to extract invariances from a set of input faces develops between 1 and 3 months

• Ability to discriminate between faces of other species can be retained through training/exposure from 3 month to 9 months of age

• Specialization for processing face stimuli at 9 months old - discriminate changes better than house stimuli

• Perceptual narrowing throughout first year of life

Visual paired-comparison task 

• aka visual preference task - measure face perception

• Infants are allowed to familiarize with one set of stimuli, which are then each paired with a novel stimuli

• The length of time spent fixated on each of the paired stimuli is measured

• Longer time on the novel stimulus indicates memory of the familiar stimulus

ERPs - general

• can measure face perception - comparison of looking at face/nonface stimuli

• N170 = ERP component observed in adults during passive viewing of faces

  • Negative deflection peaking between 140 and 170 ms after stimulus onset; most prominent over occipito-temporal scalp

  • Shorter peak latency to upright faces and larger amplitude to inverted faces

Evidence for innate facial processing

• Preferential looking in infants 

  • they don’t have any experience through which to learn

• Existence of face specific cells in 6wk monkeys

  • Exists in another species = genetic/biologically based

• Brain imaging shows activation of fusiform face area

  • Suggests this brain area is prewired to respond to faces

  • Conditions like autism with altered facial recognition show impaired activation in fusiform face area = required for facial recognition

• Prosopagnosia

  • When there is bilateral (mainly right area but left can compensate) brain damage to the fusiform area there is no longer recognition of faces - fusiform is required for this area

• Shining light faces through mother’s stomach - fetus is more likely to turn towards upright face shape than inverted

Evidence for experience based facial processing

• Plasticity

  • Brain areas need input to become specialized (activated for experts in their field - birds, cars, etc)

• Modulates face perception during development (perceptual narrowing)

  • Other race effect

• Localization increases across development

• Recognition of nonhuman primate faces is able to be trained through exposure to these faces from 3-9 months, but not with no exposure

• ERP: N170 signal is different in infants than adults

  • Infants are more sensitive to a broader array of stimuli while adults are more sensitive to faces = experience with faces = increased sensitivity

• Computer neural network models activate same areas in response to same stimuli despite having no genetic blueprint

ERP facial recognition study methods

participants: 11 adults, 34 6-month olds

Adults: viewed both species of face in both orientations

• N170 is measured via EEG

Babies: half viewed human faces in both orientations, half viewed monkey faces in both orientations

• “N170” and P400 is measured

• peak amplitude and peak latency

• chose human and monkey faces because there is a difference in capacity for recognizes monkey and human faces between infant and adults

• compared human to monkey responses and inverted to upright within species responses

ERP facial recognition study results

Adults

• N170 differed in amplitude for upright human faces

  compared to all other stimuli (smaller amplitude in upright, quicker latency), the others did not differ

• Inversion increased the amplitude/latency for human faces but not monkey

Babies

• main effect of species (amplitude of N170 was larger for human)

  • no effects of orientation or on latency

• P400: both human and monkey faces showed greater peak amplitude for upright compared to inverted

  • effect only over left side for monkeys

For adults, the orientation of the face appears to play a role in this early phase of processing, but for 6-month-old infants, the influence of orientation appears only at a later phase of processing.

Adult pattern of specialization for face processing is developed through experience

To what extent are reflexes a product of processes in the brain as opposed to the spinal cord?

• Grasping reflexes are mediated at the level of the spinal cord, but the spinal reflex center is controlled by higher brain mechanisms

  • Reflexes disappear with age as a result of the maturing of the brain and increased inhibition of the spinal reflex center from the brain

when are reflexes abnormal

 when it is absent or diminished during the period it should be actively elicitable or lasts beyond the normal age limit for its disappearance (or is exaggerated)

4 main primitive reflexes

stepping, grasping, moro, sucking

grasping plantar

• elicited by pressing a thumb against the sole of a foot just behind the toes 

• response of the reflex consists of flexion and adduction of all the toes.

• Present in first 6 months, decrease in intensity until disappear around 12-15 months

  • Commencement of standing

• Retained longer in Down’s Syndrome

• No response in congenital choreoathetosis

• Reduced in spastic CP; retained in athetoid CP

• Retained in mental retardation

• Reduced or negative plantar grasp is a sensitive indicator of later development of spasticity 

• mediated at the level of the spinal cord

grasping palmar

• inserts his or her index finger into the palm of the infant from the ulnar side and applies light pressure to the palm, with the infant lying on a flat surface in the symmetrical supine position while awake 

• The response of the reflex comprises flexion of all fingers around the examiner’s finger, which is composed of two phases: finger closure and clinging

  • Occurs as a result of pressure to tendons in the hand

• Present in first 3 months, decrease in intensity until disappears around 6 months

  • Commencement of voluntary use of hands

• inhibits moro reflex 

• Absence of this reflex usually reflects peripheral or spinal cord involvement (esp in asymmetrical cases) but can also be caused by upper brain lesions

• Reflex is increased/retained longer in spastic hemiplegia and quadriplegia

• Reflex is weak in athetoid cerebral palsy

• mediated at the level of the spinal cord

moro

•  head drop method is the most common

  • a slight drop of the infant’s head relative to the body axis in the supine position

• The initial phase of the response comprises of the extension of the arms and legs. This is then followed by the arms being brought tightly to the chest and sometimes followed by crying

• The reflex can be elicited in all infants during the first 12 weeks of age.

  • increasingly less typical with age, eventually consisting only of abduction and extension of the upper limbs.

  • Usually disappears by 6 months

• Based on the findings in normal infants, the absence or diminution of the Moro reflex within 2 to 3 months of age and the persistence of the response beyond 6 months of age can be regarded as abnormal.

• Asymmetry of response = local injury 

• Retention of the reflex is common in children with MR without motor disturbance

• mediated in the brain stem, not at the level of the spinal cord (lower region of pons to the medulla)

  • reflex is principally mediated by the vestibular nuclei (vestibular system)

  • proprioceptive inputs from the neck also contribute to elicitation of the reflex.

• movement is generated by the subcortical structures without cortical participation

• Reflex disappears with age due to increased inhibition from basal ganglia and cerebellum (upper brain structures)

absence of moro 2-3 months

• compromised condition or disorder

persistence of moro past 6 months 

• Hyperactive response in neonatal period = withdrawal from maternal drug abuse or bilateral intrauterine disturbance

stepping

• baby appears to take steps or dance when held upright with his or her feet touching a solid surface.

• lasts about 2 months

sucking

• When the roof of the baby's mouth is touched, the baby will start to suck

• This reflex doesn't start until about the 32nd week of pregnancy and is not fully developed until about 36 weeks.

• Premature babies may have a weak or immature sucking ability because of this.

• becomes voluntary at 2-4 months

rooting

• starts when the corner of the baby's mouth is stroked or touched. The baby will turn his or her head and open his or her mouth to follow and root in the direction of the stroking.

• This reflex lasts about 4 months.

reappearance of grasping reflex

• can be a result of brain lesions that result in decreased inhibition of the spinal reflex center

  • Reflexes are inhibited not lost after infancy

  • Reflex is most evident when pyramidal signs are absent

  • Frontal lobe

Reflexes and CP

• infants with cerebral palsy have been known to manifest persistence or delay in the disappearance of primitive reflexes and pathologic or absent postural reactions

• In a significant number of patients with spastic cerebral palsy, the Moro reflex cannot be elicited in the first months of life, appears subsequently in the fifth or even the seventh month, and is retained until the age of 11 months

• delay in the disappearance of the asymmetric tonic neck reflex, Moro, plantar grasp, and Galant reflexes is more conspicuous among athetoid than spastic infants

• Failure to develop postural reactions

Reflexes and MR

Normal disappearance of primitive reflexes and delayed disappearance of postural reactions

babinski sign

 the extensor toe response observed in diseases involving the corticospinal tract in older children and adults, and is considered by many authorities as the single most useful clinical reflex in neurology

• dorsiflexion of the great toe and fanning of the remaining toes

• Its presence is believed to signify frontal lobe damage or upper motor neuron disease

Physical growth and movement paper background

• Movement is as much a product of the mass, stiffness, and inertial properties of the limbs as of central neural processes

  • ex contractures

• When parents exercised their infants’ stepping reflex with daily “practice” sessions, the movement patterns in fact did not disappear, but rather increased in frequency compared to control groups

  • Could indicate inhibition from higher brain/cortical structures is not actually driving the disappearance of this reflex but disuse could be driving this

• Supine kicking movements are identical to stepping movements but do not disappear with age

  • Authors propose that this is due to the rapid growth during this time period, when held upright infants need to move their leg against gravity and if they have rapidly gained more fat compared to muscle this will be more difficult than performing the movement in a supine position where their weight is supported

Physical growth and movement paper findings

• Zero-order correlations showed that infants stepped less who gained weight most rapidly between 2 and 4 weeks (−.334, p < .05) and who showed most rapid increases in Ponderal Index between birth and 4 weeks (−.335, p < .05).

• Stepping significantly decreased in infants during a condition with additional weight added to their legs

• When placed in a condition that reduced weight constraints on the leg (water), infants stepped significantly more

  • Stronger final flexion underwater based on joint angles

• The results of these three studies suggest that rate of stepping is limited by muscle strength.

Representing moving object

• From about 4 months of age, infants predictively track an object moving on a linear path behind an occluder by shifting gaze to the reappearance position just before the object arrives there 

  • Correlated with smooth pursuit

• Success in smooth pursuit of object and saccadic jump over occluder is reliant on forming a prediction of what will happen

  • models preserve the spatio-temporal properties of the object motion

Predicting external events

• Smooth-pursuit eye movement

  • Well-timed to external motion

• When infants start reaching successfully they can catch moving objects by initiating arm and hand movements before the object is within reaching distance

Action perspective on motor development

• 10-month-old infants picked up a ball differently, depending on whether the intention was throw it into a tub or to fit it into a tube

  • Movement is driven by motivation

• infants attend to the purpose of the movements rather than their exact form

• Actions are directed to the future and must predict what is going to happen next.

  • It has to do with anticipating both one’s own posture and movements, and future events in the world

    • Controlling posture is the central role in movement production

neonatal movements are not just reflexive, but are prospective and flexible goal directed actions

• Ex rooting: If the infant touches him or herself, or is just not hungry, no rooting is initiated.

• Ex sucking: Neonates will alter their sucking in preference to their mother’s voice over another voice

Sensorimotor link between eye and hand

• Extended arm movements towards objects that are fixated on

• Bringing hands into view - ATNR reflex should be around all the time but infant fails to resist the pull if arm is not in view

• Keeping hands visible in light by waving arm

critical periods

if the area does not fully develop in those assigned periods, the developing brain does not compensate; the area is left with a deficit

rodent exposure to alcohol

exposure to alcohol during the period of high synaptogenesis (equivalent to the second and third trimesters of human pregnancy) produces several alterations in brain development, e.g. neuronal loss, altered neuronal circuitry, and apoptotic neurodegeneration in the developing forebrain

why specific timings are important in the development of different systems and organs

• Critical periods

• periods of high synpatogenesis are especially vulnerable

• “The development of the brain is a highly complex process in which the timing of events is crucial to ensure that development proceeds normally”

• Crucial periods for organ development - teratogen exposure during this time prevents typical development

  • Most organs have short crucial periods but the brain develops for so long that it is particularly vulnerable to teratogens

Characteristics of FAS

• “growth deficiency, particular facial features, and, of most concern because irreversible, central nervous system (CNS) dysfunction (mental retardation, microencephaly and brain malformations)”

• 3 criteria: (1) growth deficiency manifested by small overall height and small head size; (2) central nervous system disorders, including mental retardation and (3) a distinctive pattern of abnormal facial features. 

• Lower developmental scores on bayley’s

• Differences in astrocyte proliferation and maturation

• Loss of neurons 

• facial and growth differences improve with time

Alcohol use in pregnancy effects

• Lower developmental scores on bayleys

• FAS

• Aggression/externalizing behaviors

• Hyperactivity

• Criminality 

• Substance use disorder

• “IQ decrements and learning problems, and deficits in information processing speed”

• Even social drinking is associated with learning difficulties

• Eeg shows sensory processing is affected in FAS, fmri shows working memory issues in FAS adults

• Learning and memory dysfunction

  • “They also suggested that these are latent effects of prenatal alcohol exposure that are expressed as the central nervous system develops and matures, because the learning and memory deficits were not detected at younger ages in the same prenatally alcohol exposed offspring”

Mechanisms through which alcohol causes damage in pregnancy

•  neuron loss

• apoptotic neurodegeneration

• differences in glutamatergic receptor function in hippocampus

• compromised neural tube midline

• reductions in basal ganglia (caudate nucleus - executive control)

• corpus callosum thinning (verbal learning deficits)

• reduced cerebellar size

• alterations in HPA axis (higher cortisol)

Principles of development

• Development proceeds in a cephalocaudal direction (from head to foot).

• Development proceeds from the basic to the more specialized.

• Development proceeds in order of importance.

  • (Starts with heart and brain)

  • Starts with necessary then to general functions

behavioral states of fetus

• Behavioural states are defined as recognizable and well-defined associations of variables that are stable over time and have clear transitions between each.

  • Observed from 36 weeks

• Quiet sleep, active sleep, quiet awake, active awake