overview of the cerebral cortex: functional organization of association areas

phrenology

coin termed by Dr. Spurzheim; first attempt to localize specific functions and personality traits to different parts of the brain by feeling bumps on a person’s skull

• traits that were dominant would have larger representation in the brain and thus produce a larger bump on the skull

ventromedial region

dorsolateral region

prefrontal association areas:

ventromedial region

heavy interconnections with the limbic system via the dorsomedial thalamic nucleus; involved in emotional responses

dorsolateral region

involved with executive functions such as decision-making, planning, insight, foresight and working memory 

working memory

system that actively holds multiple pieces of transitory information in the mind where they can be manipulated

dorsolateral prefrontal cortex

involved in selection, planning and execution of the appropriate behavior in social contexts

damage to prefrontal cortex

results in difficulty carrying out complex behaviors that are appropriate to the circumstances

• impaired restraint

• disordered thoughts

• inability to plan appropriate action

lobotomy

surgery that sever the connections between prefrontal cortex and the rest of the brain

• carried out to reduce symptoms of mental disorders 

consequences of lobotomy

1. lost ability to solve complex problems

2. loss of ambition

3. inappropriate social responses

4. loss of morals

5. inability to carry out long trains of thought

6. erractic motor activity

parietal association areas

caudal to primary sensory cortex; lesion to this area results in problems paying attention to objects contralateral to the lesion

apraxia

motor disorder caused by damage to the brain, which causes difficulty with motor planning to perform tasks or movements

• typically associated with damage to the left/dominant side

neglect syndrome

inability to attend to objects, including one’s own body, in a portion of space, despite the fact that visual acuity, somatic sensation and motor ability remain intact

• typically associated with damage to the right side

• patients fail to respond to, report or orient to stimuli presented to the left side of the body; may also have difficulty performing complex motor tasks on neglected side

ideational apraxia

brain cannot make a plan for motor tasks that require multiple steps

ideomotor apraxia

common type; unable to follow directions or copy the actions of someone else

conceptual apraxia

inability to conceptualize a task and impared ability to complete multi-step actions; loss in the ability to voluntarily perfrom a learned task when given the necessary objects or tools - inability to use items for the correct purpose

limb-kinetic apraxia

you have a hard time moving fingers, arms or legs exactly the way you want; the ability to execute a sequential motor activity despite being able to demonstrate normal muscle function

apraxia of speech

hard or impossible to move your mouth/tongue to form words

egocentric deficit

deficit that can occur in contralateral neglect syndrome where an individual’s half of their visual fiel is ignored by them 

allocentric deficit

deficit that can occur in individuals with contralateral neglect syndrome where left side of all objects is ignored

right hemispheric lesion

causes severe left neglect syndrome; complete loss of ability to attend to objects contralaterally and weakened attention ipsilaterally, although it is still partially perserved due to control by left hemisphere

left hemispheric lesion

minimal right neglect syndrome; this is because the right hemisphere is intact (right parietal association areas dominate control of attention bilaterally)

broca’s area

speech production; damage to it causes motor aphasia

• located in left hemisphere 

• motor language area 

wernicke’s area

essential for interpretation of speech; located in left hemisphere

• sensory language area

superior longitudinal fasiculus

connects broca’s area with the wernicke’s areas - intrahemispheric pathway in Left hemisphere 

receptive aphasia

defect in comprehension (wernicke’s area); good spontaneous speech

anomic aphasia

word finding difficulty

• damage to wernicke’s area

motor aphasia

good comprehension, no intelligble speech; words are formed but not in a way that make sense

• damage to broca’s area 

conduction aphasia

good comprehension and spontaneous speech - poor repeititon

• damage to the superior longitudinal fasiculus

global aphasia

poor repeition and no comprehension

• damage to broca’s area and wernicke’s area

left hemisphere

dominant hemisphere

• language, speech, writing

• calculation

right hemisphere

non-dominant hemisphere; adds emotional and tonal qualities of language

• prosody and spatial perception

parietal-occipital fissure

medial cerebral cortex sulcus; defines border between parietal and occipital lobes 

calcarine sulcus

medial cerebral cortex sulcus; where the primary visual cortex is located

where pathway

connections between association areas of visual cortex with pareital lobe

what pathway

connections between assoication areas of visual cortex with temporal lobe

temporal lobe association areas

recognition and identification of stimuli that are attended to, particularly complex stimuli

• damage results in difficulty recogniing, identifying and naming different categories of objects 

• object is acknowledged, but cannot be identified 

agnosia

no knowledge; inability to interpret sensations and hence to recognize things even though sensations are intact

lesions in right temporal lobe

lead to agnosia for faces and objects

lesions of left temporal lobe

lead to difficulties with language related material (where wernicke’s area is located)

prosopagnosia

agnosia for faces