Lecture 4: A Walk Along the Cortex: I The Back Half Gordon Holmes and Holes in the Head Wilder Penfield and Brain Stimulation A map of the body-The Somatosensory “Strip” The concept of “receptive field” An Anthropologist on Mars Sacks, Oliver 305.908 Sac in 3-day loan… not req’d -but just in case… Gordon Holmes (18761966) * British neurologist (London) * patients with “penetrating missile wounds” * the “visual field” is mapped in an orderly way in the contralateral occipital lobe visual field - the region in which visual targets can be detected (tested while fixating) Visual field “defects” (“scotomas”) hemianopia - patient is unable to see in the contralateral visual field The visual pathway to primary visual cortex optic nerves - carry information from the retinal ganglion cells as far as the optic chiasm The visual pathway to primary visual cortex optic chiasm - the place where half of the information from each eye crosses over to the other side of the brain The visual pathway to primary visual cortex optic tracts - the two visual pathways from chiasm to the visual part of the thalamus The visual pathway to primary visual cortex optic radiations – “two” pathways from visual thalamus to primary visual cortex Keir et al (2004) MR imaging of the temporal Stem: anatomic dissection tractography of the uncinate fasciculus, inferior occipitofrontal fasciculus, and Meyer’s loop of the optic radiation American Journal of Neuroradiology, 25, 677–691 Wilder Penfield (1891-1976) * Canadian neurosurgeon * surgical removal of “bad bits” of cortex for treating “intractable” epilespsy * electrical stimulation of cortex in awake patients homunculous - “little man” - a representation of the body surface in a region of the brain receptive field - the area from which (and often the stimulus attributes) stimuli can influence the firing rate of a neurone Next week: Lecture A Walk Along the Cortex: II The Front Half ... attributes) stimuli can influence the firing rate of a neurone Next week: Lecture A Walk Along the Cortex: II The Front Half ... optic radiations – “two” pathways from visual thalamus to primary visual cortex Keir et al (20 04) MR imaging of the temporal Stem: anatomic dissection tractography of the uncinate fasciculus,... as the optic chiasm The visual pathway to primary visual cortex optic chiasm - the place where half of the information from each eye crosses over to the other side of the brain The visual pathway