... Responses of neurons in the primary visual cortex of a monkey to visual stimuli. (Adapted, with permission, from Hubel and Wiesel 1977.)
A. A diagonal bar of light is moved leftward across the visual field, traversing the receptive fields of a binocularly responsive cell in area 17 of visual
... Overview of the visual system as related to visual prostheses. In most retinal dystrophies, the first order photoreceptor
neurons (rods and cones) are lost. Thus, second order neurons (bipolar cells) are the earliest viable target, typically for
subretinal and suprachoroidal devices. Epiretinal devi ...
... • The “F0/F1” ratio is often used to distinguish simple (approximately linear) V1
neurons from complex (nonlinear) ones.
• Responses are recorded to sinusoidal contrast gratings. If the cell is linear, the
output should contain only the input frequency F0.
• Fourier analysis is performed on the post ...
Exam 2-SG suggested answers (2010)
... binocular neurons below the level of the cortex, while auditory pathways from from the two ears are
extensively crossed, so cells at all levels above the cochlear nuclei are binaural, i.e. they receive
inputs from both ears.
4. Photoreceptors that synapse onto ‘off’-center bipolars release depolariz ...
PSY 437 Sensation and Perception Knapp Study Guide 11 Primary
... Today we’ll trace the pathway from the retina to the primary visual cortex. We’ll also see how
primary visual cortex is organized and some things it can do..
1. What sources does each LGN receive information from and why would it be important to
receive information from these sources?
2. What type o ...
Local Cortical Circuits
... Multi-Unit Analysis
Limitations of Our Recordings Technique
Analysis of Spike Trains by Renewal Density
Visual categorization shapes feature selectivity in the primate
... Red circles : Neurons with statistically significant selectivity for diagnostic dimension only
Blue circles : Neurons with significant selectivity for diagnostic and non-diagnostic feature
Black triangles : Neurons with no significant selectivity
Red star : Example neuron depicted in previous figure ...
PPT - UCI Cognitive Science Experiments
... achromatopsia, unlike as in blindness caused by
damage to the eyes or optic nerve, even memory
of color is gone
• Akinetopsia (damage to V5 or MT)
• or motion blindness—the loss of the ability to see
objects move. Those affected report that they
perceive a collection of still images.
... Kaan Yücel M.D., Ph.D.
... diffuse illuminate because there are excitatory and inhibitory regions in receptive fields that
cancel each other out; receptive fields are not circular which do not respond well to small spots
- Cortical cells respond to stripes or edges with a particular orientation; simple cells have
Primary visual cortex
... Model of a hypercolumn showing two ocular dominance
columns (one for each eye), many orientation columns, and
the locations of the CO blobs
More Introductory Stuff
... Cells in cortex that
respond to different
Truly cool, maybe they
network together to
... outweighs inhibition, the cell may reach threshold causing another action
The cycle begins again in the next cell.
Lecture 5 - TeachLine
... What do we mean by “why” in science?
What is the primary goal of neuroscience?
Brumberg - QC Queens College
... and the role that sensory experience has in shaping cortical circuits. In a new line of research,
further work focuses on the interaction between the neural and vascular systems
Our results have shown that neurons participating in different pathways (eg. callosal –
connecting the two hemispheres ver ...
KC Kajander GJ Giesler, Jr. KJ Gingrich JH Byrne YS Chan J
... S. Warren, H. A. Hamalainen, and E. P. Gardner, “Objective classification of motion- and directionsensitive neurons in primary somatosensory cortex of awake monkeys.” It was incorrectly stated that
Orban and co-workers (J. iVeurophysioZ. 45: 1059-1073, 198 1) attributed direction selectivity to cort ...
... 1. Light hyperpolarizes the rod and
excites the bipolar cell below it
2. But inhibitory connections through
horizontal cells suppress signals
3. Best response to localized “dot”
4. While stimulating surround only
lowers firing rate
What is this???
Convolution!!! Im*[-1 2 –1]
... Three-dimensional schematic of a portion of the cerebral cortex. The pieces are from the postcentral and and precentral gyri. Within the cortex are six
layers in which cells and their processes are located. A. Lamination pattern of neurons from the somatic sensory cortex (postcentral gyrus) is shown ...
... The hippocampal synaptic circuit is important for declarative memory. Information arrives in the hippocampus from entorhinal cortex through the perforant
pathways, which provide both direct and indirect input to CA1 pyramidal neurons, the major output neurons of the hippocampus. (Arrows denote the
Feature detection (nervous system)
Feature detection is a process by which the nervous system sorts or filters complex natural stimuli in order to extract behaviorally relevant cues that have a high probability of being associated with important objects or organisms in their environment, as opposed to irrelevant background or noise. Feature detectors are individual neurons – or groups of neurons – in the brain which code for perceptually significant stimuli. Early in the sensory pathway feature detectors tend to have simple properties; later they become more and more complex as the features to which they respond become more and more specific. For example, simple cells in the visual cortex of the domestic cat (Felis catus), respond to edges – a feature which is more likely to occur in objects and organisms in the environment. By contrast, the background of a natural visual environment tends to be noisy – emphasizing high spatial frequencies but lacking in extended edges. Responding selectively to an extended edge – either a bright line on a dark background, or the reverse – highlights objects that are near or very large. Edge detectors are useful to a cat, because edges do not occur often in the background “noise” of the visual environment, which is of little consequence to the animal.