PSYCH 375 midterm 2

Greeble study

• several properties that are also associated with faces (consider whether you think this helps or hurts their argument after we discuss the results)

• They show inversion effects

• Seem to be processed configurally,

• categorized at token level

• Before ‘training’ (to recognize/ categorize the stimuli), the FFA does not respond strongly to stimuli

• After many hours of training, the FFA produces a robust response to those stimuli

• Suggests acquiring perceptual expertise with these stimuli led to recruitment of the FFA

Replicated greeble study

• replicated the above experiment with a prosopagnosic patient and found they were eventually able to reach ‘expert’ status (albeit they required more trial than controls to achieve this)

• They were thought to use alternative strategies to compensate for their deficit, as we’ve discussed happens in other contexts

Ventral stream

(inferotemporal, or IT, cortex) that are important for object identification of various kinds (these are around the ventral stream):

• FFA

• Parahippocampal place area

• Extrastriate body area

• Visual word-form area

Parahippocampal place area

Selectively responds to places/scenes/landscapes

Extrastriate body area

Selectively responds to body parts

Visual word-form area

Selectively responds to words

Damage to Parahippocampal place area

associated with difficulty recognizing places/scenes/landscapes (topographic agnosia)

FFA fMRI study

measured a signal that is thought to be closely related to the BOLD signal (oscillatory power in the Gamma band) and, like that signal, reflect higher rates of synaptic activity

• They found similar results as with fMRI (e.g. elevated activity in the FFA when viewing faces)

• they were also able to directly stimulate the FFA and observe (in real-time) what impact that had on the perceptual experience of the patient fitted with the ECoG

• The patient reported that stimulation of the FFA resulted in a distortion to his perception of faces in the room (but nothing else), supporting the idea this region plays a causal role in the perception of faces

Capgras syndrome

involves a delusional belief that someone they know (usually someone important, e.g. friends, partners, family members, etc.) has been replaced by an ‘imposter’, or ‘doppelgänger’

• Can cooccur with various forms of pathology (brain damage, dementia, schizophrenia, etc.)

• On some level, this involves a deficit in object (/person) identification and can therefore be likened to various forms of visual agnosia that we’ve already discussed

• At the same time, the fact that those affected can still perceive the people as at least resembling their true identity implies different underlying mechanisms

• intact conscious/explicit processing but impaired unconscious/implicit processing

Two neural pathways mediate recognition of familiar faces

• covert/implicit

• Overt/explicit

Explains why some people with prosopagnosia, while being unable to explicitly identify faces, may nevertheless show some sign of implicit recognition using galvanic skin response (GSR)

Capgras underlying mechanism

• hypothesized that abnormal (impaired) connectivity between the inferotemporal cortex and the amygdala may be responsible

• More generally, various differences in connections between the temporal lobe and limbic system may contribute (potentially representing another example of a disconnection syndrome)

• Given the role played in memory for structures in/around the medial temporal lobe (such as the hippocampus, more on this soon!), it has also been speculated that deficits in the retrieval of episodic memories in particular may also be involved

Reduplicative paramnesia

involves a delusional belief that a familiar location has been duplicated

• associated with damage to temporal areas

  • And damage to frontal areas

Fregoli delusion

involves the belief that multiple individuals who are presented as distinct people are in fact the same person

• This can manifest as thinking that someone has transformed themselves into another form, adopted a disguise, and/or are able to occupy multiple bodies

• may believe this (singular) person is transforming in order to trick them, manipulate them, do them harm, etc., and often involves paranoid thoughts revolving around persecution

Fregoli delusion Brain

• damage to frontal and temporal-parietal areas

  • Maybe abnormal activity in memory relevant areas (inappropriate reaction)

  • Evidence for reduced inhibition

  • Abnormal dopamine may contribute

Delusions

• overactivity of dopaminergic systems

  • Schizophrenia

  • Amphetamine-induced. Psychosis

FFA MVPA within cetagory correlations

how does the distributed pattern of activation when viewing faces in one subset of the data (even numbered trials) compare to viewing faces in another subset of the data (odd numbered trials)?

FFA MVPA between category correlations

how does the distributed pattern of activation when viewing faces in one subset of the data (even numbered trials) to viewing tools in another subset of the data (odd numbered trials)?

Long term memory

• declarative memory

  • Episodic and semantic memory

• Non declarative memory

  • Procedural memory

  • Priming

  • Simple classical conditioning

  • Habituation & sensitization

Petersen et al 1988

compared activation during word blocks with fixation blocks (i.e. used subtractive logic)

• Note that it is not clear what (exactly) participants were doing during the fixation block, as well as the fact that they may have encoded things during those blocks (not necessarily related to the stimuli but maybe just the context, e.g. ‘this is super boring!’)

• the possibility discussed in an earlier lecture that participants in FFA fMRI studies may have approached the presentation of faces (vs. houses, for example) differently when spontaneously (and with minimal experimental instructions) shown stimuli from each category

Tulving et al 1994

• Based on the logic described on the previous slide, showed participants a set of photos on day 1, then brought them back for a follow-up session on another day (day 2)

• Two kinds of photos were presented on day 2: an ‘old’ condition (involving photos that were shown on day 1), as well as a ‘new’ condition (involving photos that were not shown on day 1)

• It was predicted that more encoding would take place while viewing new stimuli, as compared to old, which would be reflected in differences in neural activation

• They found greater hippocampus and parahippocampal activation during the presentation of ‘new’ stimuli, as compared to ‘old’

Incidental encoding

said to occur when encoding proceeds automatically, or without specific intention (e.g. have you ever read something that ruined a game, show, movie, etc. that you wanted to watch later?)

• The vast majority of what we encode probably falls under this category

Stern et al 1996

showed 40 novel images with instructions to encode them for a later test

• Compared activation in a ‘one-item’ condition in which only a single image is presented on each trial, to that in a ‘many-items’ condition in which several images are presented on each trial (with the trial duration being held constant across conditions)

• Found greater activation in the ‘many-item’ condition, as compared to the ‘one-item’ condition, within several regions (including posterior hippocampus, parahippocampal gyrus, and fusiform gyri)

ERP used to study incidental encoding

1. Present a series of stimuli, one at a time

2. Average ERP’s time-locked to stimulus onset

3. Test memory of participants for stimuli

4. Compare ERP’s recorded during initial stimulus presentation, as a function of subsequent memory performance

Advantage of incidental coding

is that participants are doing the thing on each trial, so that should reduce the chances of various confounds (that could apply to the previous designs we‘ve already talked about), e.g. boredom, differences in basic perceptual demands, etc.

Disadvantage of incidental coding

However effects using this paradigm provided difficult to replicate, with methodological differences (e.g. in the form the test took, i.e. free recall vs. cued recall vs. recognition) further complicating interpretations

Remember judgment

• episodic recollection for memory

Know judgment

• encountered information factually (semantic memory)

• Familiarity can be associated

Wagner et al 1998 fMRI memory brain

Found left hemisphere activation

• verbal processing confound

Brewer et al 1998 fMRI memory brain

responses associated with higher confidence involved bilateral parahippocampal gyrus activation and right dorsolateral PFC

• visual processing confound?

Wagner and Brewer memory brain studies results speak to

the role that verbal and visual processing play in supporting encoding, which (once again!) highlights the difficulty in isolating signals related to a singular dimension of what may tend to be a multidimensional process

Ranganath et al 2005, fMRI incidental encoding instructions

1. Present line drawings of novel 3D shapes for 7-13 seconds, followed by memory probe (that was the same as the sample on 50% of the trials)

2. Conduct a surprise memory test (i.e. incidental encoding)

3. Sort the fMRI data as a function of performance on the memory test

Ranganath et al 2005, fMRI incidental encoding results

• Found that activation in the left dorsolateral PFC and left hippocampus shortly after stimulus presentation predicted performance

• Objects presented during the memory test that were correctly responded to were associated with greater activation in those areas during initial processing

• Between subjects: On a subject-by-subject basis, the magnitude of the ‘memory effect’ (i.e. change in left hippocampus during the early delay period) was correlated with later memory performance

• Among other things, demonstrates the power of taking an individual differences approach

Ranganath et al 2005, functional connectivity analysis

Found that more successful encoding (as indexed by behaviour) was associated with greater functional connectivity between the hippocampus and many other MTL regions

Inconsistent hippocampus evidence factors:

• Methodological confounds that don’t reflect it’s true activity level (e.g. subtractive logic may ‘wash out’ contributions that happen throughout the entire experimental session)

• Limited neural resources: We can’t encode everything and things that we find more compelling, exciting, etc. may compete for those resources, leaving relatively little for whatever may be the intended target of encoding

• Hippocampal contributions to other kinds of processing (e.g. spatial navigation)

Hippocampus role

• memory & Spatial cognition

• Mid posterior = spatial navigation

• Anterior = memory

Maguire, Woolett, Spiers (2006)

compared a group of London taxi drivers with a group of London bus drivers. Can we see differences in spatial navigation?

• Used volume-based analyses (VBA), which produces volume estimates (of certain brain regions)

• Provide a well-matched comparison (socioeconomic status, nature of work, various perceptual and physiological factors relating to driving, etc.)

• The key difference is the requirement for taxi drivers to be able to flexibly navigating a complicated environment (which bus drivers don’t have to worry about, given the way bus routes work)

• Found that the taxi drivers had more gray matter in mid-posterior hippocampus, and less in anterior hippocampus, as compared to the bus drivers (tradeoffs?)

Optic flow

the faster you drive, the faster the relative motion seems to appear. Relative to you theres relative movement

- can judge speed based on flow.

Volume-based analysis

Looking at volume or size of structures which may not align perfectly in differences in connectivity

• if there are neuroplastic changes— Mighhht see a bigger area in those that use skill more?

Tulving distinct forms of memory

• autonoetic

• Noetic

• Anoetic

Noetic

(knowing) can occur with or without feelings of familiarity

• Can be broadly related to semantic memory

Autonoetic

(self-knowing) refers to instances that match a description in which retrieval

• relates to episodic memory, ideas of recollection and mental time travel

Anoetic

not knowing

• Can be broadly related to non-declarative/implicit memory

• e.g. effects related to procedural memory, conditioning, priming, etc.

Dual process of explaining emotional response

one subcortical pathway generating a rapid and automatic emotional response, one cortical pathway generating a slower and more controlled emotional response

Familiarity and recollection dual process

• Free recall is thought to depend on recollection

• Recognition can be supported by familiarity

• thought to have complimentary properties and therefore often work together to facilitate retrieval

Recollection

• depended on by free recall

• Involved with the retrieval of various associations involving qualitative information

• A relatively slow process

• An all or nothing process

• Closely associated with hippocampal processing

Familiarity

• supports recognition

• Involved with a quantitive memory signal that gauges how likely it is that stimuli had been previously encountered

• Rapid and relatively automatic

• Something that varies along a continuum (not ‘all or nothing’, a quantitive signal)

• Supported by various neocortical regions of the MTL (including the perirhinal cortex)

Process of familiarity and recollection

1. You might recognize someone from a movie who looks familiar, without having made any effort to attend to or identify them (familiarity signal kicks in)

2. Associations with the person may start coming back to you (places, times, etc.), even before you can identify who they are and/or being trying to do so

3. More controlled effort focusses your attention on memories related to those associations, beginning a more deliberate attempt to identify them (recognition processing kicks in)

4. If successful, those recognition processes will match your perception of the person to something in memory, and lead you to interpret/impose some meaning on the stimuli

Semantic memory

is defined as memories for facts whose retrieval is not accompanied by information pertaining to how, when, or where that information was acquired – its retrieval is noetic.

Mental lexicon

Knowledge of the word meaning

H.M.

didn’t show semantic deficits after removal of his hippocampus

• Early evidence that semantic is a distinct memory system from episodic

• Also suggested an intact MTL system is not necessary for retrieving semantic representations

Semanticization

gradual shift in the nature of memories from episodic to semantic

• lose episodic content

Spreading activation

think about one experience at your elementary school and you may spontaneously start thinking about others without intending to (i.e. a priming effect)

Cognitive model of semantic knowledge

• spreading activation from clusters/nodes

Warrington and McCarthy

suggested that brain damage can result in a

selective impairment related to animacy (i.e. living things vs. objects)

• Patient V.E.R. had a left hemisphere stroke, demonstrated severe linguistic

impairments, and showed relative impairments in identifying various non-living

things

• 4 patients (inc. J.B.R., S.B.Y., Warrington & Shallice 1984) with herpes

encephalitis showed relative impairments in identifying living things

• Some of these patients had lost the ability to speak and relied on pointing to

communicate, though some also retained the ability to speak (seeming to rule

out the possibility this deficit related to a more general language deficit)

Evolutionary pressures have resulted in

specialized mechanisms for perceptually and conceptually distinguishing animate and inani­mate kinds … leading to a categorical organization of this knowledge in the brain.

Warrington and Shallice (1984)

suggested the aforementioned case studies may be more accurately described as involving a distinction related to action and perception

• e.g. Patient J.B.R. showed deficits related to living things, as well as several categories of non-living things (e.g. musical instruments, fabrics, etc.)

• According to this view identifying living things primarily involves vision, while identifying non-living things tends to rely on our knowledge of how we use those objects

Modality specific knowledge hypothesis

suggests a key organizational factor in the use of semantic information is the ‘functional modality’)

• One line of supporting evidence comes from self-reported ratings indicating what properties participants feel they rely on to identify various kinds of objects (Hoffman & Ralph, 2013)

Martin et al 1996 PET

contrasted brain activity during the silent naming of animals and tools

• Results seemed consistent with a modality-specific model discussed earlier:

• Animal naming was associated with greater activation in visual cortex (due to a role in processing low-level visual features)

• Tool naming was associated with greater activation in areas related to action generation: posterior middle temporal gyrus and premotor cortex

Posterior middle temporal gyrus

• role in processing motion

Premotor cortex

• a role in processing movement, and/or mirror neuron activity

Caramazza and Shelton 1998

suggested distinctions between animals vs. fruits/ vegetables vs. artifacts (e.g. tools)

• “these, and only these, three categories form the basis for the organization of conceptual knowledge”…evolutionary pressures [that] led to specific adaptations for recognizing and responding to animal and plant life”

Post-hoc

consists of statistical analyses that were specified after the data were seen

Anomia

Deficit in object naming (linguistic or semantic memory impairment or both?)

Semantic dementia

describe patients with anomia (implying that the difficulty in object naming is related to more general problems with the semantic memory system)

Fluent primary progressive aphasia

emphasizes the role of language specifically (and may not implicate the semantic memory system at all)

Semantic Dementia framework

• involves two somewhat distinct systems that can be independently affected in various dementia patients: Associative agnosia due to pathology in the inferior temporal cortex (i.e. Adlam et al., 2006) & Aphasia due to pathology in the left hemisphere perisylvian language cortex (i.e. Mesulam, 2003)

• damage to the inferior temporal cortex, simply by way of functional connectivity with the perisylvian language cortex, could result in both linguistic and non-linguistic deficits alike (Mummery et al., 1999). Thus, it might not be possible to cleanly dissociate the two entirely from one other given their close functional relationship

Adlam et al 2006

tested patients with early-stage fluent primary progressive aphasia

• Used voxel-based morphometry (VBA), which allows estimates of grey matter density (white matter = myelinated axons, grey matter = neuronal bodies, astrocytes, dendrites, etc.)

• They found that the extent of bilateral degeneration in the anterior temporal lobes of these patients predicted both verbal and non-verbal performance deficits

• This suggests a close functional relationship between these two parts of the brain

• In other words, even if parts of the brain involved in language processing are intact, linguistic deficits may arise from damage to more distant regions that may provide input that is critical for the ability of those areas to function 'normally’

Petersen et al 1998 PET role of language in object knowledge

used PET to demonstrate greater activity in left inferior PFC while generating verbs, as compared to either hearing/repeating words, or reading aloud visually presented words

• This was interpreted to mean that region may be important for semantic processing, independent of input modality

Theories from cognitive psych and linguistics arguing about localizing semantic knowledge in the brain

The meaning of a concrete noun is not unitary, but rather is com­posed of parts – specifically, knowledge about the physical and functional properties of the object.

Computation and neural models suggest long term memories

are made of up of associations between many regions (such as sensations, emotions, actions, etc.)

Martin et al 1995 isolating contributions made to object knowledge by colour and action

• Presented black and white line drawings of common objects to participants in one of three conditions:

1. Name the objects

2. Name a colour associated with the object

3. Name an action that could be performed with the object

• subtracted the data (fMRI images) associated with the object naming condition from the colour or action conditions

  • colour condition - object naming condition = isolated contribution of colour to object knowledge (independent of verbal labels)

  • action naming condition - object naming condition = isolated contribution of action to object knowledge (independent of verbal labels)

• In theory, this produces the following contrasts which isolate contributions of these two properties to object knowledge

• Action naming activated parts of the brain near regions which are important for processing motion and other perceptual-based qualities

• Colour naming associated with activity in part of ventral temporal cortex (near a region in ventral occipital cortex involved with processing colour)

• Both tasks activated parts of left PFC and premotor cortex (PMC)

Synaesthesia

involves the reliable, automatic, and involuntary triggering of a specific perceptual experience when processing a specific sensory stimulus

• Various explanatory theories involving things like abnormal activation of pathways (functional connectivity), abnormal connections (structural connectivity), neural pruning, etc.

Colour-grapheme synaesthesia

people perceive alphanumeric characters as appearing in specific colours (regardless of what colour they are actually presented in),

Paulesu, Harrison, Baron-Cohen, and Watson (1995) Synaesthetes

• used PET scanning to detect activation when synaesthetes heard spoken words and tones

• Words were chosen that were known to trigger the perceptual experience of colour in the synaesthetes

• The synaesthetes (but not controls) showed greater activation when hearing words in several areas, including the ventral temporal regions implicated in the colour-naming task in Martin et al. (1995)

Challenges to neuroimaging work

• Design/interpretation often heavily influenced by case studies

• How can we disentangle language and meaning (i.e. can we represent meaning without language?)

• More generally, how can we know whether the tasks we choose are appropriately and selectively recruiting the processes we want to study?

Repetition suppression affects fMRI

can sometimes be observed where the BOLD response gradually declines with the repeated presentation of stimuli that have some kind of commonality (e.g. the same colour, shape, from the same conceptual/ semantic category, etc.)

• Although somewhat distinct in terms of the neurological mechanisms involved, this is conceptually similar to desensitization and habituation

fMRI adaptation paradigm

can be used to attempt to determine what properties a given brain region responds to, based on the presence (or absence) of these effects

• For example, if we find a region that shows repetition suppression effects when presented with multiple pictures of different dogs, that could be taken as evidence the region is tuned to respond to the ‘concept’ of dog (not the low level physical properties inherent to the stimuli, e.g. colour, shape, etc.)

Grill-Spector, Henson, and Martin (2006) used repetition suppression effect

To make inferences about what parts of the brain are sensitive to higher-level meaning (e.g. conceptual category), as compared to low level stimulus properties (e.g. colour)

• In other words, they were looking for parts of the brain that recognized (‘treated') pictures of things from categories of stuff that were previously presented as belonging to that same category

This consisted of two phases:

1. Study phase: 32 items were shown, all of which were also presented again during the test phase, referred to as ‘same’ items

2. Test phase: Three types of stimuli presented, described on the next slide

Grill-Spector, Henson, and Martin (2006) repetition suppression effect - TEST PHASE

Some items were the same: pictures that were shown during the study phase (e.g. the same picture of a dog you saw earlier)

• Some items were slightly different (same type but different token): exemplars from the same category as something that was shown in the study phase (e.g. a different dog)

• Some items were completely novel: pictures that were unrelated to anything shown during the study phase (e.g. a house, if nothing house-like was shown during the test phase)

Grill-Spector, Henson, and Martin (2006) repetition suppression effect - three regions results

• demonstrated:

  • Suppression for same items

  • Release from suppression for the different and novel items

• Interpreted as indicating they were sensitive/responding to low-level visual features of stimuli (e.g. shape, lighting, etc.)

Grill-Spector, Henson, and Martin (2006) repetition suppression effect - left fusiform gyrus results

• showed

  • suppression for same items

  • release from suppression for novel items

  • only a partial release from suppression for the different items

• Interpreted as indicating that region’s role in recognizing the conceptual similarity (somewhat independent of low-level visual features)

• May implicate a role for that region in a modality-independent form of semantic representations

Contextual reinstatement

involves first activating knowledge about more general properties and then using that general knowledge to focus your memory search (e.g. what was I doing last night? Well I usually eat dinner in the evening, let me think about what I ate last night, where I was, etc.…)

• related to Encoding specificity principle

Polyn et al 2005 MVPA incidental encoding task stages

1. Study phase: view 90 stimuli from 3 categories (famous people, famous locations, common household objects) while making various judgments (how much do you like this person, how much would you like to travel here, how often do you use this object)

2. Training phase: a neural network pattern classifier was trained to distinguish between the distributed pattern of neural activity associated with each stimuli

3. Free recall phase: during the (surprise) memory test, participants were instructed to recall as many items as possible while the pattern classifier attempted to ‘guess’ what category an item being recalled belonged to

Polyn et al 2005 MVPA incidental encoding task results

• Their pattern classifier was able to successfully interpret which of three categories items that were being recalled belonged to

• Groups of items from a particular category were recalled in tightly packed groups, or clusters

• Demonstrates contextual reinstatement

• These clusters are presumed to underlie various kinds of shifts in brain state and suggest these kinds of large-scale fluctuations are important for facilitating retrieval

Modal memory

which conceived of short-term memory (STM) as simply being a passive buffer that allows for the temporary retention of information that hasn't been committed to long-term memory

Working memory

proposed as a system that can both temporarily hold onto information, as well as manipulate/ process that information (in a way that wasn’t account for in the STM model)

Memory systems may be supported by

• Prolonged neural activation related to mechanisms involved with direct perception (e.g. activity in visual cortex)

• The activation of semantic representations

• Regions/networks involve with cognitive control

digit span test

Used to measure short term memory. Can memorize typically 7±2 numbers

• HM was able to keep things active in STM indefinitely via rehearsal