Cortical areas Flashcards
Hubel and Wiesel (1974)
Injected tritiated amino acids into adult monkey eye then performed autoradiography and found in layer 4 of V1, alternating patches of 500μs. Suggests ocular dominance columns
o Just anatomical and no physiological measures here
Poggio et al (1988)
): Recorded single neurons in V1 of rhesus monkeys with stereoscopically presented luminous bars and dynamic dot patterns and found 2 sets of stereotypical neurons. One tuned 0/near0 and another cross and uncrossed, where uncorrelated input both eyes would drive these neurons. Suggesting a neural correlate of stereopsis but likely implemented higher up.
Hubel and Weisel (1962)
Recording of V1 neurons in anaesthetised cat and found to populations of neurons. Simple cells have ON and OFF spatially mapped out and then complex cells that have orientation selectivity but not linear RFs and they receive input from simple cells and LGN and have motion selectivity.
Stettler et al (2002)
Functional mapping using recombinant adenovirus with GFP to label axons of V1 found that intrinsic connections link similarly oriented domains in the V1 and so intrinsic horizontal connections likely provide a more likely substrate for contour integration.
Beck et al (2011)
Used 2 photon imaging to characterise orientation selectivity in group of neurons in mouse V1 and found that inhibitory IN that converge onto excitatory V1 neurons with widely varying preferred orientations, suggesting that this pooling of information could be used to modulate the gain of orientation cells
o Did not classify the IN subtypes, 51% of synapses onto inhibitory targets where as in cats and macaques been reported only 10-20% so variance across species and role/influence of inhibitory neurons may not be conserved across animals
Cowey (1964)
Stimulating the V2 responses and applying a stimulating electrode in V1 in a V1 macaque (striate-prestriate boundary) and found that as moved stimulating electrode around, found a correspondence of position across the V1 and V2 boundary so topographic relation which seems like a mirror image.
o Didn’t know it was the V2 at the time
James et al (2003)
Patient DF. Anatomical MRI showed that lesion corresponded bilaterally to LOC in healthy participants and that fMRI showed a lack of activation with line drawings that mirrors poor performance in identifying the objects depicted in drawings but robust activation in streams during object grasping.
Alfraz et al (2006)
Electrical microstimulation to small clusters of IT neurons while monkey perform categorisation task and found that to face selective sites but not other sites, stimulation strongly biased the monkeys decisions towards the face category suggesting a correlate between activity of face-selective neurons and face perception
Riesenhuber and Poggio(1999)
Proposed the HMAX mosel describing a hierarchical model that extends from model of simple and complex cells and based on physiological data of the IT. It reflects the assumption that invariance of position and scale and feature specificity must be built up through separate mechanism
Murphey et al (2009)
Whether detectable percepts could be produced by electrical stimulation of intracranial electrodes over human visual areas identified with fMRI
o Stimulation of early visual areas including V1, V2, and V3 was almost always detected, whereas stimulation of late visual areas such as FFA was rarely detected
o When percepts were elicited from late areas, subjects reported that they were simple shapes and colors, similar to the descriptions of percepts from early areas. There were no reports of elaborate percepts, such as faces in areas like FFA
o For sites eliciting percepts, the detection threshold was determined → Current
Movshon et al (1996)
Recording neurons in the V1 and MT in response to plaid and pure gratings which reveal that while MT responds to global motion of plaid patterns, V1 only responds to individual orientation components and that all V1 projections to MT were direction selective. This supports that V1 processes basic features that are then built up into more complex representations
Newsome and Pare (1988)
By making lesions in V5 using ibotenic acid caused elevations in motion thresholds for dynamic random dot display but had little effect on contrast thresholds thus indicating that MT contributed selectively to perception of motion.
Rust et al (2006)
Shoed that responses of MT cells can be captured by a linear-nonlinear model that operates not on the visual stimulus bit on afferent responses of a population of nonlinear V1 cells which robustly predicts responses to gratings and plaids. Cells that signal pattern motion are distinguished by having convergent suppression and a tuned normalisation that may reflect suppressive input from the surround of V1 cells
Salzmann et al 1990
Electrical stimulation of neurons in V5 of rhesus monkey and measuring the effects on psychophysical performance on direction of motion of a visual display. Found that stimulation biased the animals judgement towards the direction of motion encoded by the stimulated neuron
• Kiani et al (2007):
recorded from over 56000 neurons in monkey IT with over 1000 natural and artificial objects to look at correlation in the response across the population and found that categorical structure of objects is represented by the pattern of activity distributed over the cell population such as clusters for bodies, hands and faces and these were further divided into human and monkey faces. This suggests there are an inherent categorical representation
