3.6 - association cortical functions

allocortex

older part of brain

• abt 10% of cortex

• 3-4 layer organization

neocortex

latest part of brain

• 90% of cortex

• 6 layers - inside out = grey outside, white inside

what are the most common neuronal morphology in the neocortex?

stellate + pyramidal

where are the upper motor neurons located in the neocortex?

layer V

what are the 3 major neocortical input + output courses?

1. cortex

2. thalamus

3. subcoritcal structures

3 sections of neocortex layers

• supragranular = 1-3

• internal granular = 4

• infragranular = 5-6

supragranular layers

layers 1-3

• intracortical comm.

• and thalamic inputs in layers 1 + 3

internal granular layers

layer 4

• thalamic inputs

• subcortical

infragranular layers

layers 5-6

• corticospinal output

• thalamic input + output

• subcortical

white matter

myelinated axons

• mediate communications btw cortex + subcortical

3 types of projection in white matter

1. commissural fibers

2. association fibers

3. projection fibers

commissural fibers

connect hemispheres

• corpus callosum

association fibers

communicates w/in 1 hemisphere

• superior longitudal fasciculus (SLF)

projection fibers

connects cortex + subcortical structures

• internal capsult

4 major cortical lobes

frontal, parietal, temporal and occipital

primary cortex

• motor, vestibular, somatosensory, visual, auditory, olfactory and gustatory cortexes

• function = direct processing of single type of sensory stimulus or motor command

• area = abt 20% of cortex

association cortex

integrate multiple sensory + motor stimuli w/ memory + emotion

• create complex behaviors:

  • learning

  • emotional response

  • language

  • planning + making decision

parietal lobe functions

• spatial awareness

• sensory-motor coordination

• attention

parietal lobe mode of action

visual, auditory, vestibular, somatosensory inputs

→ premotor, motor and skeletal muscle cortexes

parietal left lateralization

left-right awareness

• object recognition?

• calculation?

• language

parietal left damage consequences

• Gerstmann’s syndrome = left-right confusion

• inability to percieve objects

• Wernicke’s projections = difficulty writing + speaking

• inability to calculate

parietal right lateralization

attention + spatial awareness

parietal right damage consequences

• difficulty drawing + construction

• contralateral neglect of body + space (usually left)

• unaware of spatial awareness deficits

parietal mediated behaviors

1. awareness of body parts for movement coordination + paying attention

• walking, eating, in a lecture

2. awareness of space+ objects around body

• finding places, dancing w/o stepping on partner’s feet, crossing street safely, object + its trajectory

temporal lobe functions

• lagnuage

• verbal memory

• facial recognition

temporal mode of action

visual + auditory inputs

→ premotor, motor and skeletal muscle cortexes

→ language

temporal left lateralization

dominant in speech

• processing + identification of auditory info

• language recognition + verbal memory

temporal left damage

• less verbal memory

• less language/ word recognition

temporal right lateralization

• proess + identify non-verbal info

• facial recognition + visual/ music memory

temporal right damage

• hard to recal visual + music

• hard to recognize ppl

• persistent talking

frontal lobe functions

memory, planning, personality

• executive center of the brain

• 33% of cortical area

• most recently evolved brain region

• last to develop during brain development

frontal lobe mode of action

inputs from all parts of brain

→ premotor, motor and skeletal muscle cortexes

→ complex behavior

frontal mediated behaviors

1. behavior + personality

• behave based on social norms

• suppress impulsive behaviors

2. complex emotions

• can feel empathy + sympathy

• understands humor, sarcasm + deception

3. higher level cognition

• comprehension, problem solving, planning, creativity + decision making

frontal cortex lesion

• motor ability

• loss of fine movements + strength in limbs + fingers

• loss of facial expression

frontal cortex lesion

• cognitive ability

• decreased problem solving ability

• memory loss

• difficulty in language execution

• reduced creativity

frontal cortex lesion

• social ability

• lack of drive

• more impulsive

• increased irritability

• impaired moral judgement

schizophrenia

depressed frontal lobe activity

• disordered thought process, impaired problem solving ability

• unusual speech + behavior

ADHD

decreased frontal lobe activity

• inattention, unfocused, hyperactive + impulsive

OCD

abnormally high activity in orbital frontal cortex

• persistent urges that cause distress/ anxiety or repeated behaviors that feels driven to perform

brain compartmentalization

neurons that perform the same or similar fuction cluster together in brain

• primary cortical areas

brain integration

neurons from different brain regions communicate w/ each other to accomplish

• association cortical areas

contralateral brain fuction

each brain hemisphere controls opposite side of body

• right side of brain controls left side of the body

lateralized brain fuction

2 side of brain NOT equal (hemisphre dominance or lateralization)

• advantage = allows for greater # of functions

• disadvantage = no back up, lesions may cause permanent loss of function

Broca’s area

involved in speech production

Wernick’s area

speech planning + comprehension

if the left hemisphere is damaged, can people still speak?

yes, the right hemisphere is also involved in speech

• unclear whether same centers are in the right

patients w/ right temporal lesions lose ability to ________

comprehend + generate prosodic speech

bilingual vs. monolingual left lobe

• primary languagee = use both areas

• secondary learned early = use same Wernicke’s different Broca’s

pathway when responding to spoken words

1. sound

2. auditory cortex

3. Wernicke = recognize words + formulate speech

—arcuate faciculus →

4. Broca = plan pronunciation

5. motor cortex activates muscles to pronounce words

pathway when reading written words out loud

1. eye

2. visual cortex

—angular gyrus →

3. Wernicke = recognize words + formulate speech

—arcuate faciculus →

4. Broca = plan pronunciation

5. motor cortex activates muscles to pronounce words

wernicke’s aphasia

• fluent but meaningless speech

• difficulty in language comprehension

broca’s aphasia

• short but meaningful speech

• limited vocab

• difficulty speaking and writing

voluntary attention (endogenous)

• top-down process

• docused on particular task

• guided by goal + expection

• visual-dorsal stream

reflexive attention (exogenous)

• button-up process

• involuntary response to stimuli

• not planned or goal-driven

• visual-ventral stream

which parts of the brain are involvd in attention?

frontal, parietal and temporal cortices

2 classes of ADHD symptoms

1. inattention

2. hyperactivity/impulsivity

causes of ADHD

• delayed brain development

delayed brain development (especially frontal lobe)

→ delayed learning, planning and restraint

causes of ADHD

• decreased brain activity

1. decreased frontal lobe

• low: glucose metabolism, blood flow + neuronal activity

2. decreaed parietal neuronal

causes of ADHD

• altered brain connectivity

more connected to reflexive than voluntary