Functional Specialisation

Functional specialisation  Broca and Wernicke’s area. o Paul Broca was presented with a patient who could understand language but could not speak. Post-mortem examination showed lesions in the posterior region of the frontal lobe (Broca’s region), now known to be associated with motor control of speech. o Karl Wernicke described a patient who could speak, but not understand language. Following post-mortem examination, it was found that there were cortical lesions located in the posterior part of the temporal lobe (Wernicke’s region), now known to be associated with interpretation of language.  Brodmann’s areas. o Cerebral cortex is divided into ~50 distinct areas called Brodmann’s areas. o Their distinction is made based on histological structural differences. o Mapping of the brain is useful in determining the functional areas in the human cortex. o Areas 1 – 3 constitute primary somatosensory area. o Areas 5 – 17 constitute somatosensory associated area. Homunculus  Somatotopic organisation of sensory and motor cortices.  Areas of these cortices are devoted specifically to the sensory or motor control for certain areas of the body.  The homunculus shows which section of the cortex is responsible for sensory and motor control of which area of the body, as well as the relative proportion of cortex that this particular body part occupies. o Extensive sensory: hand, lips and face. o Extensive motor: hands and jaw. Association areas  Neurons and neuronal processes in the association lobes are much more complex than in the primary cortices.  They receive sensory, visual and auditory information (located in the parietal lobe). o Visual information from occipital lobe. o Auditory information from temporal lobe.  After receiving information, they compile and associate sensory information.  While primary neurons would fire under any stimulus of their corresponding receptors, association neurons may only fire if there is a combination of information/stimuli (e.g. reaching for object while visually fixated on it).  The complexity of association areas is evident in cases of lesions.  In this case, there may be hemispheric neglect (e.g. if asked to reproduce a flower, the patient believes they have completed the task but have actually neglected an entire half of the picture). Prefrontal specialisation  Higher level functions are associated with information integration.  In the frontal lobe, this information includes: o Memory. o Multiple tasks. o Mentalising. o Personality (the case of Phineas Gage). Agnosias  Inability to interpret sensations, therefore, recognise things.  Associated with damage to certain parts of the brain. Agnosia Tactile agnosia Area Effected Left of right anterior parietal lobe (posterior to primary somesthetic area) Cortical neglect Right superior parietal lobe – may extend to occipital lobe Appreceptive visual agnosia: 1. Right and left inferior occipital cortex 1. Acquired 2. Right and left inferior occipital cortex and achromatopsia posterolateral temporal cortex 2. Progsopagnosia Associative visual agnosia Occipitotemporal cortex (bilateral) Balint syndrome 1. Left and right superior occipital cortex 1. Visual disorientation 2. Ocular apraxia 3. Optic ataxia Auditory agnosia Amusia Speech/language disorder Wernicke’s aphasia Anomic aphasia Alexia with agraphia Pure alexia (no agraphia) Broca’s aphasia Global aphasia Conduction aphasia Subcortical aphasia Aprosodia 2. Posterior parietal cortex 3. Posterior parietal cortex Posterior and superior temporal cortex (bilateral) Right posterior superior temporal cortex Area Effected Left posterior superior temporal cortex (Wernicke’s area) Left parietal lobe (posterior to Wernicke’s area) Wernicke’s area and left angular gyrus Left occipital lobe and associated commissural fibres (either in underlying white matter of splenium of corpus callosum) Left frontal operculum (Broca’s area) Enire left perisylvian area (frontal, parietal and temporal opercula) Left inferior parietal lobe (supramarginal gyrus) and underying arcuate fasciculus Head of left caudate nucleus Right perisylvian area (frontal, parietal and temporal opercula) Hemispheric specialisation  Although there is extensive connectivity, each is highly specialised in its own right.  Left side: o Language. o Calculation.  Right side: o Drawing. o Music. o Spatial perception. Basal ganglia and cerebellum Learning objectives  To understand the anatomy and physiology of basal ganglia.  To understand the anatomy and physiology of the cerebellum.  Sensory inputs can come: o Directly from the spinal cord. o By cortical pathways through structures like the basal ganglia and cerebellum.