THE OCCIPITAL LOBE

Function: Vision: perception of form, movement and color.

OL

Separated from parietal lobe by:Parieto-occipital sulcus. Within the OL 3 landmarks:•Calcrine fissure: Div. The upper and lower halves of the visual world.•Lingual Gyrus: V2 & VP•Fusiform Gyrus: V4

Subdivisions of the OL (6+ Areas)

OL

1. V1

2. V2

3. V3

4. V3A

5. V4

6. V5

Primary VisualCortex

Secondary VisualCortex

V1 Largest area, called striate cortex. Receives the largest input from the LGN and projects to ALL other occipital regions. 1st processing level.

V2 Also projects to all other occipital areas. Segregates info from V1.

V1

V2V3 (A)V4V5

V2

V1V3 (A)V4V5

OLConnections

2 Pathways into the visual brain

OL

Eye

LGN V1V2

Dorsal (ParL)“How” or Where”

Visual Guidence of mov.

1

Ventral (TempL)“What”

Obj. perception & recog.

Tectum(Sup Colli)

Pulvinar(Thal)

Medial

Lateral2

1. Geniculo-striate system2. Tecto-pulvinar system

Connections cont…

Visual processing in humans does NOT culminate in the Secondary visual ares (V3, V4, V5) but continues within multiplevisual regions in the parietal, temporal and frontal lobes.

Beyond the Occ. LOL

OLTheory of O.L FunctionV1 & V2 function like mailboxes: segregating info to other areas

involved in the perception of: Color/Form/Motion

V3 Dynamic form (dancing)V3A Just form

V4 Color & ShapeV5 Perception of motion

V2 Like V1 but less severeV3 Perception of form is affected

V1 If everything else intact, Ss act like if they were blindbut visual input still gets through the other areas (V2)“BlindSight”

V4 Vision in gray shadesV5 Can’t perceive objects in motion

Selective Lesions Affect specific functions

OLTheory of O.L Function Cont…

5 Types of visual functions

1. Vision for action: Visual processing required to direct specific movements.

2. Action for vision: Active search of the target object. Selective attention.

3. Visual Recognition: Ventral stream infoto the temporal lobe specialized in recognition of faces “Grandmother cells”

Grandma!

OLTheory of O.L Function Cont…

5 Types of visual functions

4. Visual Space: Visual info comes form specific location in space. Objects have a location relative to an individual (egocentric),

or to one another (allocentric).

5. Visual Attention: Process of features of the visual world (otherwiseit would be too much!).

Dorsal & Ventral stream functions OL

Milner & Goodale studies

Patient DF: Blind but dorsal streamintact, so patient shaped her handAppropriately while reaching.“Unconsciously” see locationsize and shape.

Patient VK: Ventral stream intact,Can see objects but can’t reachAccurately or shape the hand.

OL

1. Agnosias2. Monocular Blindness3. Bitemporal Blindness

Symptoms of OL Damage

6. Quadrantanopia7. Scotoma

4. Nasal Hemianopia5. Homonymous Hemianopia

1. Object Agnosiaa) Apperceptiveb) Associative

2. Other visual AgnosiasAlexiaVisual-spatial agnosia

Prosopagnosia:

1. Object Agnosiaa) Apperceptive agnosia: Can’t recognize an object although basic visual functions (color, motion etc.) are preserved. Can’t copy or match simple objects. Can see one thing at a time: Simultagnosia. Diffuse bilateral lesion in the ventral stream in OL.

b) Associative agnosia: Can’t recognize objects in spite of being to perceive them. Subjects can describe the object, know what it is for, copy it, but can’t identify it. Lesion in ventral stream in TL.

Symptoms of OL Damage Cont… OL

OL

•Function of OL is vision, perception of form movement and color.•Three major routes: ventrally into the temporal lobe, dorsally into the parietal lobe, and a middle route going to the STS.•Ventral stream for stimulus recognition, dorsal stream for guidance of movements in space.•Some occipital regions are functionally asymmetrical: word recognition on the left and facial recognition and mental rotation on the right.

Summary:

THE PARIETAL LOBE

v

PLFunction: Processes and integrates somatosensory and visual info

with regard to the control of movement.

Separated from the frontal lobeBy the central fissure, from the Temporal lobe by the SylvianFissure and from the occipitalLobe by the parieto-occipitalSulcus.

PL

Within the PL:•Postcentral gyrus (B.A. 1,2,3)•Par Operculum (B.A. 43)•Superior Par Lobule (B.A. 5,7)•Supramarginal gyrus (B.A. 40)•Angular gyrus (B.A. 39)

Anterior Zone: Includes:Postcentral gyrus and Par OperculumCalled: Somatosensory cortex. ProcessesSomatic sensation and perception.Posterior Zone: Includes:Superior Par Lobule, supramarginal &angular areas. Called: Posterior ParietalCortex. Processes control of movement with somatic and visual info.

Subdivisions of the PL

PL

von Economo’s maps 3 PP areas:PE, PF, PG

Connections1. The somatosensory cortex projects to PE, primary motor cortex, Supplementary and premotor areas. For tactile recognition, sensory info about limb position in the control of movement.

S1

PEM1SupMPreM

PLConnections cont…2. PE output to M1 to guide movement with tactile information, input

from S1 (1,2,3).3. PF output to M1 to guide movement with tactile and visual info

input from S1 through PE.4. PG output to FL. Main dorsal stream, vision for action control of

spatially guided behavior. Input from visual, somesthetic, proprioceptive,auditory, vestibular, oculomotorand cingulate.

PLConnections cont…5. PG output to paralimbic for memory of movements6. PG & PF output to PFC for STM of visual guided movements.7. PG output to temporal for processing the shape of objects

So, the APC processes somatic sensation and perception and the PPC integratessensory input from the somatic and visual regions for the control of movement.

PLTheory of P.L Function

There must be a spatial (internal) representation of things. There is amap or several maps that:

•Make movements to different objects•Discriminate similar objects•Make movements relative to body position•Order the movements•Attend to some objects and ignore others

Other aspects of PL function:

1. Arithmetic: Math has quasi-spatial nature, you have to manipulatenumbers in space. Left tempo-parietal.

2. Language: Also quasi-spatial demands: “tap” “pat” same lettersdifferent spatial organization

3. Understanding sequences of movement

PLSomatosensory symptoms(anterior zone, areas 1,2,3,43)1. Somatosensory thresholds:

2. Perceptual Disorders

3. Blind touch4. Somatosensory agnosias:

2. Simultaneous Extinction: objects can only be perceivedif presented one at a time R>L

PL

Neglect follows a RPPLx because the integrationof the spatial properties of stimuli becomes disturbed. Although stimuli are perceived, theirlocation is uncertain to the CNS= ignore it.

Posterior Parietal Symptoms(PE, PF, PG)

1. Balint’s syndrome2. Contralateral neglect3. Object recognition:4. Gerstmann syndrome5. Language deficits

7. Recall deficits8. Acopia9. Spatial Attention10. Spatial Cognition11. Attentional shift for action12. Mental imaging6. Apraxia: a.Ideomotor

b. Constructional

PL

Neuropsychological Assessment

THE TEMPORAL LOBE

TLFunction: Processes visual and auditory information, and integrates

them for emotion, spatial navigation and spatial and objectrecognition.

Includes all the tissue that lies below the Sylvian sulcus and anterior to theOL. Includes subcortical structures:limbic cortex, amygdala, andhippocampus.

TLSubdivisions of the TLWithin the TL:• Superior Temporal Gyrus: multimodal receiving inputs from auditory, visual and somatic regions as well as from the FC, PC and paralimbic cortex.

• Middle Temporal Gyrus: (Limbic cortex). Includes the amygdala, uncus, hippocampus, subiculum, entorhinal and perirhinal cortices and the fusiform gyrus.

• Inferior Temporal Gyrus: (Visual regions). Includes the fusiform gyrus, called TE.

TLConnectionsThe TL receives afferents from the sensory systems, and sends efferents to parietal, frontal, limbic system and basal ganglia.5 distinct types of cortico-cortical connections:

1. Hierarchical sensory pathway: From primary and secondary visual and auditory areas. Ventral stream. For stimulus recognition.

2. Dorsal auditory pathway: From auditory areas to PPC. For detecting spatial localization of auditory inputs.

3. Polymodal Pathway: parallel projections from the visual and auditory association areas into the STS. For stimulus categorization.

TLConnections cont…

4. Medial Temporal projection: from the visual and auditory association areas into the medial temporal or limbic. Called: perforant pathway. For long term memory.

AA perirhinal entorhinal hippocampus amygdala

5. Frontal lobe projection: from the visual and auditory association areas into the FL. For movement control and short term memory.

TLTheory of TL FunctionOn the basis of cortical anatomy 3 basic sensory functions:1. Processing of auditory input2. Visual object recognition3. Long term storage of sensory input (memory)

The TL is a WHAT system for auditory and visual info that is going to:1. Identify2. Categorize3. Store4. Give affect

TLTheory of TL Function cont…

The STS and biological motions: species typical movements,necessary for social perception. E.g. dogs sniffing each others butt

The STS analyzes these type of movements. Necessary for socialCognition = the development of hypotheses about the intentionsof other Ss. = Theory of Mind

Ss with RTL can’t do theory of Mind and their personalities are “sticky”: egocentric andnegative.

TLSymptoms of TL Damage

1. Disturbance of auditory sensation and perception2. Disorders of music perception3. Disorders of visual perception4. Disorders in the selection of visual and auditory input5. Impaired organization and categorization of sensory input6. Inability to use contextual information7. Impaired LTM8. Altered personality and affective behavior9. Altered sexual behavior

TLSymptoms of TL Damage cont…

1. Disturbance of auditory sensation and perception

A. Language

Formants: Frequency or sound waves specific toeach vowel sound. “Ba” “Ga” “Da”

Context: “Duck” and “deer” we perceive it as thesame although the formant is different.

Speed: Language is fast, we categorize the sounds

Left TLLx more affected

2. Disorders of music perceptionThe brain has neural networks dedicated to the processing of language and music = both are biological processes.Proof: neanderthal flute, infants have preferences for music, congenital amusia (tone deafness).RTLLx more affected, RTL is necessary to distinguish melodies.

TL

Neuropsychological Assessment