What is the strongest reason for thinking that the first self-replicating life-form was not a protein?
Matters of the Mind: the Neuron and Beyond Notes Week 6 Ventral Stream Most of the 30 visual areas are in this stream Hasson and colleagues o fMRI: viewing a film Event related action potentials Findings: selective activation to precise movement- to-movement film content in temporal lobe areas o Fusiform face area Lights up when you see faces o Parahippocampal place area Lights up when you see places Tanaka and colleagues o Hyper-complex cells Cells in area of TL require complex features for activation (diff faces) o Vertical columns Similar selectivity Minimize the effect of small changes to allow categorization o Experience-dependent specificity Specificity of neurons is altered by experience Gauthier and coworkers (1999) o Everyone has different facial features o We focus on faces because they are of importance to us D.F.’s damage to LO area Blind to certain objects but could shape her hands to pick up objects Dorsal stream intact o Can understand things to orient body to correct movements o “Unconsciously see location, shape, and size” Visual agnosia o Different lesions create bewildering variety of symptoms o Lack of agreement on how different patterns of varying symptoms should be classified (taxonomy) o Object agnosia 1. Apperceptive Intact basic visual functions Deficit in the ability to develop a perceptive of the structure of an object or objects (like DF) Perceptual problems Regions sending output to ventral stream Carbon monoxide poisoning in “water-shed” regions 2. Associative Can perceive objects (copy and draw) but cannot identify them Memory not perception Results from lesions to the anterior and medial temporal lobes (objects have no meaning) Double blood supply helps fight strokes in the watershed regions Medial temporal lobe: limbic system Amygdala and septum o Emotion and species typical behaviors Hippocampus o Memory and spatial navigation The dorsal Dorsal stream damage causes hands to not be able to use an object A theory of parietal lobe function Anterior zones (1,2,3) o Somatosensory strip o Processes somatic sensations and perceptions Posterior zones (the rest) o Integrates vision to motor cortex to plan movement o Integrate everything together o Integrate info from vision with somatosensory info for control of movement Case V.K.: parietal damage and visuomotor guidance Bilateral hemorrhages in occipito-parietal regions Could not form appropriate hand postures Initially blind ut after 1 month had Balint’s syndrome o Disorder control of gaze, impairment in visual attention (simulatognosia: only one object) and optic ataxia o Ataxia: lack of voluntary coordination of muscle movement o Optic ataxia: deficit in visually guided hand movements An ‘older’ pathway Geniculostriate pathway o Goes through V1 Damage (functionally blind) Tectopulvinar o Goes through this pathway with blindsight Info sent to parietal lobe but wasn’t sent to V1 so he wasn’t conscious that he could see V1 and Blindsight Blindsight or cortical blindness o Evidence of vision processing without conscious awareness o You have no conscious vision but can process info without being conscious B.K. o Could perceive location in hindsight o Couldn’t see images but could point to them D.B. o Can report movement orientation and location of objects o Provides evidence that not all info has to go through V1 G.Y.: Emotion and blindsight 44 year old male Emotional faces presented in both (damaged/undamaged fields) Areas activated in undamaged fields o Facial recognition o Emotion Amygdala (emotion regulator) R hemianopia o Damage to left V1 Possible explanations o Dorsal pathway spared o Tectopulvinar pathway used Zombie in the brain Movements that you don’t consciously think about Superior Temporal sulcus (STS) Imaging reveals activation in the STS during perception of biological motion Biological motion o Movements relevant to a species o Social cognition or “theory of mind” Understanding others intentions from their body movements David Perrett and colleagues o STS cells are maximally responsive to particular types of biological motion Eye gaze, mouth and eye movement, facial expression, hand movements