Presentation on theme: "THE OCCIPITAL LOBE. Function: Vision: perception of form, movement and color. OL Separated from parietal lobe by: Parieto-occipital sulcus. Within the."— Presentation transcript:
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 Visual Cortex Secondary Visual Cortex
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 V2 V3 (A) V4 V5 V2 V1 V3 (A) V4 V5 OL Connections
2 Pathways into the visual brain OL Eye LGNV1V2 Dorsal (ParL) “How” or Where” Visual Guidence of mov. 1 Ventral (TempL) “What” Obj. perception & recog. Tectum (Sup Colli) Pulvinar (Thal) Medial Lateral 2 1.Geniculo-striate system 2.Tecto-pulvinar system Connections cont…
Visual processing in humans does NOT culminate in the Secondary visual ares (V3, V4, V5) but continues within multiple visual regions in the parietal, temporal and frontal lobes. Beyond the Occ. L OL
Theory of O.L Function V1 & V2 function like mailboxes: segregating info to other areas involved in the perception of: Color/Form/Motion V3Dynamic form (dancing) V3AJust form V4Color & Shape V5Perception of motion V2Like V1 but less severe V3Perception of form is affected V1If everything else intact, Ss act like if they were blind but visual input still gets through the other areas (V2) “BlindSight” V4Vision in gray shades V5Can’t perceive objects in motion Selective Lesions Affect specific functions
OL Theory 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 info to the temporal lobe specialized in recognition of faces “Grandmother cells” Grandma!
OL Theory 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 (otherwise it would be too much!).
Dorsal & Ventral stream functions OL Milner & Goodale studies Patient DF: Blind but dorsal stream intact, so patient shaped her hand Appropriately while reaching. “Unconsciously” see location size and shape. Patient VK: Ventral stream intact, Can see objects but can’t reach Accurately or shape the hand.
OL 1. Agnosias 2. Monocular Blindness 3. Bitemporal Blindness Symptoms of OL Damage 6. Quadrantanopia 7. Scotoma 4. Nasal Hemianopia 5. Homonymous Hemianopia 1.Object Agnosia a) Apperceptive b) Associative 2.Other visual Agnosias Alexia Visual-spatial agnosia Prosopagnosia:
1.Object Agnosia a) 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
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:
v PL Function: Processes and integrates somatosensory and visual info with regard to the control of movement. Separated from the frontal lobe By the central fissure, from the Temporal lobe by the Sylvian Fissure and from the occipital Lobe by the parieto-occipital Sulcus.
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 Operculum Called: Somatosensory cortex. Processes Somatic sensation and perception. Posterior Zone: Includes: Superior Par Lobule, supramarginal & angular areas. Called: Posterior Parietal Cortex. Processes control of movement with somatic and visual info. Subdivisions of the PL
PL von Economo’s maps 3 PP areas: PE, PF, PG Connections 1. 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 PE M1 SupM PreM
PL Connections 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, oculomotor and cingulate.
PL Connections cont… 5. PG output to paralimbic for memory of movements 6. 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 integrates sensory input from the somatic and visual regions for the control of movement.
PL Theory of P.L Function There must be a spatial (internal) representation of things. There is a map 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 manipulate numbers in space. Left tempo-parietal. 2.Language: Also quasi-spatial demands: “tap” “pat” same letters different spatial organization 3.Understanding sequences of movement
PL Somatosensory symptoms (anterior zone, areas 1,2,3,43) 1.Somatosensory thresholds: 2. Perceptual Disorders 3.Blind touch 4.Somatosensory agnosias: 2. Simultaneous Extinction: objects can only be perceived if presented one at a time R>L
PL Neglect follows a RPPLx because the integration of the spatial properties of stimuli becomes disturbed. Although stimuli are perceived, their location is uncertain to the CNS= ignore it. Posterior Parietal Symptoms (PE, PF, PG) 1.Balint’s syndrome 2.Contralateral neglect 3. Object recognition: 4. Gerstmann syndrome 5. Language deficits 7. Recall deficits 8. Acopia 9. Spatial Attention 10. Spatial Cognition 11. Attentional shift for action 12. Mental imaging 6. Apraxia: a.Ideomotor b. Constructional
TL Function: Processes visual and auditory information, and integrates them for emotion, spatial navigation and spatial and object recognition. Includes all the tissue that lies below the Sylvian sulcus and anterior to the OL. Includes subcortical structures: limbic cortex, amygdala, and hippocampus.
TL Subdivisions of the TL Within 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.
TL Connections The 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.
TL Connections 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. AAperirhinalentorhinalhippocampus amygdala 5. Frontal lobe projection: from the visual and auditory association areas into the FL. For movement control and short term memory.
TL Theory of TL Function On the basis of cortical anatomy 3 basic sensory functions: 1.Processing of auditory input 2.Visual object recognition 3.Long term storage of sensory input (memory) The TL is a WHAT system for auditory and visual info that is going to: 1.Identify 2.Categorize 3.Store 4.Give affect
TL Theory 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 social Cognition = the development of hypotheses about the intentions of other Ss. = Theory of Mind Ss with RTL can’t do theory of Mind and their personalities are “sticky”: egocentric and negative.
TL Symptoms of TL Damage 1.Disturbance of auditory sensation and perception 2.Disorders of music perception 3.Disorders of visual perception 4.Disorders in the selection of visual and auditory input 5.Impaired organization and categorization of sensory input 6.Inability to use contextual information 7.Impaired LTM 8.Altered personality and affective behavior 9.Altered sexual behavior
TLSymptoms of TL Damage cont… 1. Disturbance of auditory sensation and perception A. Language Formants: Frequency or sound waves specific to each vowel sound. “Ba” “Ga” “Da” Context: “Duck” and “deer” we perceive it as the same although the formant is different. Speed: Language is fast, we categorize the sounds Left TLLx more affected 2. Disorders of music perception The 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.