Association cortices

Motor Sensory Association

Somato Sensory Pathway

Sensory Cortex Receptive Field

Two Point Discrimination

Columnar organization of somatosensory cortex

Sensory Cortex

somaticProprioceptive

Area 5 integrates tactile information from mechanoreceptors in the skin with proprioceptiveinputs from the underlying muscles and joints.

This region also integrates information from the two hands.

Area 7 receives visual as well as tactile and proprioceptive inputs, allowing integration of stereognosticand visual information.

The posterior parietal cortex projects to the motor areas of the frontal lobe and plays an important role in sensory initiation and guidance of movement.

Association Cortex Information Flow

Pattern of Vibration of the Basilar Membrane

The Auditory Cortex

Discrimination of Sound “Patterns” by the Auditory Cortex

Pathways to the somatosensory, visual, and auditory association areas

Visual Pathway

AIT = anterior inferior temporal area; CIT = central inferior temporal area; LIP = lateral intraparietal area; Magno = magnocellular layers of the lateral geniculate nucleus; MST = medial superior temporal area; MT = middle temporal area; Parvo = parvocellular layers of the lateral geniculate nucleus; PIT = posterior inferior temporal area; VIP = ventral intraparietalarea.) (Based on Merigan and Maunsell 1993.)

Pathways to the somatosensory, visual, and auditory association areas

Unimodal sensory inputs converge on multimodal association areas

Interaction Among Association Areas Leads to Comprehension, Cognition, and Consciousness

Emotion Localization

Parietal Lobe

Left Hemisphere

Cortical Sensory Loss

Disorder of language

Fluent aphasia, alexia

Gerstman’s syndrome (Angular gyrus)

acalculia,

finger agnosia,

left/right disorientation,

agraphia

Tactile agnosia (bimanual asteriognosis)

Bilateral Ideomotor & ideational apraxia

Right hemisphere

Cortical Sensory Loss

Topographic disorientation

Topographic memory loss

Anosognosia /dressing apraxia

Constructional apraxia

Hemi-inattention

Apraxia of eye opening

Confusion

“Attention Neurons” in the Monkey Parietal Cortex

Attention activity of Right Parietal Cortex in Normal

Contralateral Neglenct Syndrome

Temporal Lobe

Either Temporal dysfunction

Auditory– Threshold of brief auditory stimuli elevated – Spoken words less clear– Distorted words are less clear– Difficulty in equalizing sound presented to both ear– Rapidly presented words and number in both ear difficult to

perceivingHallucination

– Auditory,– visual, – olfactory and

– gustatoryEmotional and behavioral changesDelirium

Left temporal dysfunction

Auditory deficits (right ear) – Intracranial localization of sound is impaired. – Increased threshold for perception of short bursts of sound. – Increased threshold for some frequencies. – Failure to perceive brief simultaneous auditory stimulation.

Visual deficit (both eyes) – Upper right quadrantanopsia.

Other complex sensory deficits – Right hand tactile performance difficulty. – Right hand finger agnosia.

Left temporal dysfunction

Language deficits – Decoding of speech sounds (phonemes) is impaired. – Problems with verbal repetition. – Problems with auditory comprehension of speech. – Receptive aphasia (deficits in all language qualities). – Impairment of dichotic listening to verbal material. – Intellectual impairment on verbally mediated intellectual

processes.

Memory impaired for verbal material.Emotional disturbances

– Perceptual distortions, alterations of mood, obsessionalthinking, psychosis, temper outbursts, hypo and hypersexuality

Right Temporal dysfunction

Right temporal lesion effects tend to be notable statistically but of less clinical significance.

1.Visual analysis (nonverbal primarily)– Impairment of simple and complex

visual analysis, but some negative findings.

– Impairment of short-term nonverbal memory.

– Impaired perception of tachistoscopically-presented letters.

– Prosopoagnosia (especially with anterior lesions).

– Impaired recognition of objects seen from unusual angles

3. Auditory analysis (nonverbal) – Impairment of short-term auditory

memory.

– Perception of short sounds impaired.

– Impaired recognition of familiar sounds.

– Impaired tonal discriminations, timbre discriminations, and amplitude discriminations.

– Amusia. – Impairment of contralateral ear

input in dichotic listening.

Right Temporal dysfunction

4. Constructional tasks – Visual construction impairment

proportional to tissue loss. – Impairment in maze learning

(visual and proprioceptivefeedback).

– Enlarged left-hand margin in dictation.

5. Psychiatric personality phenomena with right temporal epilepsy – Personality changes. – Psychiatric symptoms. – Deja vue. – Metamorphopasias.

6. Psychometric findings– Temporary decline in

Performance IQ following lobectomy.

– Impairment on WAIS Picture Arrangement.

– Impairment on Binet Memory for Designs

– Possible impairment of WAIS Block Design?.

7. Persistence in maintaining a hypothesis even after being informed it was not correct.

Bitemporal dysfunction

Human bitemporal lesion– Kluver bucy like + aphasia, amnesia and bulimia

Bilateral inferior and medial temporal lesion– Sham rage like – React to every stimuli with extreme belligerence, screaming, cursing ,

biting and spitingBilateral post cortical lesion

– Cortical deafness – unaware of deafnessKorsakoff amnesic defect

Selective activation of face cells in the inferior temporal cortex of a rhesus monkey

Prosopognosia

Occipital Lobe

Unilateral occipital lesion

Contralateral (congruent) homonymous hemianopia, may be

central (spitting the macula or peripheral

Homonymous hemiachromatopsia

Elementry unformed hallucination – irritative lesions

Left occipital lesion

Right homonymous hemianopia

Alexia and color naming defect with deep white matter or

splenium of corpus callosum involved

Visual object agnosia

Right occipital lesion

Left homonymous hemianopia

Visual illusion, (metamorphopsias), and hallucinations

Loss of topographic memory and visual orientation

Bilateral occipital lesions

Cortical blindness

Anton syndrome

Loss of perception of color

Prosopognosia and simultagnosia

Balint syndrome

Balint Syndrome (Bilateral parietooccipital region)

An inability to look voluntarily into the peripheral field, with normal

eye movements (psychic paralysis of fixation gaze)

A failure to precisely grasp or touch an object under visual

guidance, hand and eyes in- coordinated (optic ataxia)

Visual inattention affecting mainly the periphery of the visual field,

attention to other sensory stimuli being intact

Failure to properly direct occulomotor function in the exploration of

space (amorphosynthesis)

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