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PSYD50 notes 2.docx

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Jonathan Cant

Article #1: The Fusiform Face Area : A Module in Human Extrastriate Cortex Specialized for the Face Perception The hypothesis of this study was that the Fusiform gyrus is the specialized area for face perception Past studies suggested that face and object recognition involve qualitatively different processes that may occur in distinct brain areas. In macaques, neurons in the superior temporal sulcus (STS) respond specifically to faces. Studies were also conducted on patients with epilepsy: (In fusiform and inferotemporal gyri) N200 potentials have been elicited by faces but not other images ( scrambled faces, cars…) From the gathering of many studies, there is evidence for specialized neural modules for face perception in extrastriate cortex. Three parts to the study : 1. Experimenters looked for a region of interest on subjects. A specific area that is more responsive to faces than to objects 2. Experimenters tested to see whether “face areas” were responding to low level features in faces but not in non face stimuli. Also tested whether the “face area” was distinguishing between different exemplars of a single class of objects. 3. Tested whether the region of interest against various questions: Would the ROI respond to : - faces viewed at an angle, faces with concealed external features ( Hair), hands, and faces: when attention is directed at another task Subjects: 20 normal subjects, under the age of 40 ( five were omitted due to head motion) Stimulus: 90 freshman ID photographs, 90 object photographs, 90 house photographs Part 1: During each stimulus epoch, 45 different photographs were presented at a rate of 1 per 670 ms. - subjects were instructed to maintain fixation during non stimulus epochs ( or in stimulus epochs) and to look solely at the stimuli. Part 2: to study the low level hypothesis, subjects were presented with two tone versions of photographs ( showed in part 1) and scrambled versions of the same photographs. - scrambling preserves average luminance of intact faces and other low level features. - To study the exemplar hypothesis, they presented subjects with two tone versions of photographs, although this time they presented photographs of houses instead of scrambled faces. - Part 3: Comparison 1: passive viewing of ¾ faces vs. hands (full attention) - Comparison 2: passive viewing of ¾ faces vs. hands ( divided attention) Results: Evidence that fusiform fires specifically to faces Fusiform does not fire in response to low level features of faces in scrambled face stimuli, all category exemplars, all animate or human items or attention distracting stimuli Future studies: Other areas in face recognition might be involved because some subjects showed activation in the medial temporal gyrus and in superior temporal sulcus. -There might be regions of the cortex that are specialized for functions involved in face processing. While fusiform needed for global processing, face processing more holistic than object processing - distinguishing between face processing and processing individual parts (eg. Nose) Article #2: Expertise for cars and birds recruits brain areas involved in face recognition Hypothesis: Expertise with unfamiliar objects („greebles‟) recruits face selective areas in the fusiform gyrus (FFA) and occipital lobe (OFA) Neurological studies suggest that the brain areas responsible for face and object processing can be dissociated. Studies suggest that the extra striate cortex contains a map of visual features, and the same region cannot process different object categories when features of the objects differ. Other research suggests that level of categorization and expertise account for a large part of the activation between faces and objects This experiment
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