Untitled Flashcards Set

what is prosopagnosia?

1. the inability to distinguish among faces; associated with damage to the fusiform face area

2. studies show that people with prosopagnosia can have different responses to familiar vs unfamiliar faces, displaying unconscious recognition

describe visual neglect

1. Visual Neglect: The inability to attend to or respond to stimuli in the visual field contralateral to a parietal lobe lesion.

   1. i.e. left parietal lobe damage so the person cannot respond to stimulus from their right eye

what spectrum of electromagnetic radiation are humans capable of seeing? what wavelengths of light do we detect?

1. Visible light ranges from 400nm (purple) to 700 nm (red)

what is the first anatomical structure light hits on its way to the retina?

1. Cornea: the clear, outer surface of the eye that plays a crucial role in focusing images by bending incoming light

what cell type does light hit first in the retina?

1. The retina is, in a sense, inside-out. Light passes through several cell layers before reaching its receptor

2. Ganglion cells or photoreceptors (most likely photoreceptors)

what photoreceptors function in the dark?

1. Rods

what are dark conditions called?

1. Scotopic

what photoreceptors function in bright light? what is bright light condition called?

1. Cones; Photopic

photoreceptors for color vision? motion detection?

1. Cones for color vision

2. Rods for motion detection

what is retinitis pigmentosa? what are its symptoms ?

1. The retina begins to degenerate at the periphery, causing tunnel vision and eventually blindness.

   1. hereditary diseases involving the progressive death of photoreceptors and degeneration of the pigment epithelium

2. Symptoms: decreased night/low light vision and loss of side vision

what are the different theories of motion vision? how does trichromatic differ from opponent-process?

1. Duplexity theory of vision: cones & rod mediate different kinds of vision.

2. Component Theory (Trichromatic Theory): Proposed by Young, refined by Helmholtz

   1. Three types of receptors, each with a different spectral sensitivity

   2. S-cones detect short wavelengths, M-cones detect medium wavelengths, L-cones detect long wavelengths

3. Opponent-Process Theory: Retinal ganglion cells use an opponent-color system. Neurons respond to opposing pairs of primary colors

   1. Retina contains two kinds of color-sensitive ganglion cells: red-green and yellow-blue

describe receptive fields in the retina?

1. Receptive fields are areas of the visual field within which it is possible for a visual stimulus to influence the firing of a given neuron.

2. The retina has two types of center-surround receptive fields

   1. On-center Ganglion Cell: This ganglion cell responds most when light strikes the center of its receptive field and is inhibited when light strikes the periphery.

   2. Off-center Ganglion Cells: These ganglion cells respond the most when light strikes the periphery and are inhibited when light strikes the center.

what’s the visual pathway from retina to cortex?

1. Retina: photoreceptors, bipolar cells, ganglion cells

2. Optic Nerve: axons of ganglion cells form the optic nerve which exits the eye at the optic disc, creating a blind spot

3. Optic Chiasm: the optic nerves from both eyes partially cross; info from the right visual field is processed by the left side of the brain, and vice versa

4. Lateral Geniculate Nucleus (LGN) of the thalamus (also has center-surround receptive fields)

5. Primary Visual Cortex (V1 or Striate Cortex) in the occipital lobe

   1. first brain area to receive visual info from the LGN

   2. Contains specialized receptive fields

      1. Simple cells: Respond to lines of a specific orientation at a specific location within their receptive field.

      2. Complex cells: Respond to lines of a specific orientation moving in a particular direction, regardless of location within their receptive field.

      3. Hypercomplex cells: Respond to lines of specific length, orientation, and angles

6. Extrastriate cortex: includes areas like V2, V3, V4, and V5 (also known as the middle temporal area or MT)

   1. Processes more complex visual information through two streams:

      1. Dorsal stream ("where" pathway): Processes spatial information, such as location and movement, traveling from the magnocellular layers of the LGN through V1 to V2, V3, V5 (MT), and finally to the parietal lobe.

      2. Ventral stream ("what" pathway): Processes object recognition and color information, traveling from the parvocellular layers of the LGN through V1 to V2, V4, and finally to the inferior temporal lobe

at the optic chasm, what fibers cross over and what fibers do not?

1. Axons from ganglion cells in the nasal retina (the part of the retina closer to the nose) cross over at the optic chiasm.

2. Temporal fibers (part of the retina closer to the temple) do not cross over

what happens if we damage area V5? what’s that disorder called?

1. V5 aka the Middle Temporal Area plays a key role in motion perception

2. Damage to area V5 can result in a condition called akinetopsia, also known as motion blindness

when would an off-center ganglion cell send the highest rate of firing? when will that be most active?

1. when light strikes the periphery of its receptive field while the center remains dark

what are the different layers of the Lateral Geniculate Nucleus (LGN)? Where do they receive their innovation from?

1. The LGN is organized into six distinct layers, each receiving input from only one eye:

   1. Layers 1, 4, and 6: These layers receive input from the contralateral eye (the eye on the opposite side of the body).

      1. i.e. the left LGN's layers 1, 4, and 6 receive input from the right eye.

   2. Layers 2, 3, and 5: These layers receive input from the ipsilateral eye (the eye on the same side of the body).

      1. i.e. the left LGN's layers 2, 3, and 5 receive input from the left eye

2. The LGN also has magnocellular & parvocellular layers:

   1. Magnocellular Layers (Layers 1 and 2): contain neurons with larger cell bodies. They receive input primarily from M-cells, a type of ganglion cell in the retina that is sensitive to movement and low-intensity light.

      1. processes motion, depth, and spatial location info

   2. Parvocellular Layers (Layers 3, 4, 5, and 6): contain neurons with smaller cell bodies. They receive input primarily from P-cells, a type of ganglion cell in the retina that is sensitive to color, fine detail, and static or slow-moving objects.

      1. processes color, form, and texture info

what are the cells in the vertical pathway of the retina? the horizontal pathway?

1. Vertical pathway: photoreceptors —> bipolar cells —> retinal ganglion cells

2. Horizontal pathway: horizontal cells and amacrine cells

where is visual pigment made? where is it stores?

1. visual pigments are molecules that absorb light and initiate the process of photo transduction.

2. They are made in the inner segment of photoreceptors and then stored in the outer segment

in the dark, what are photoreceptors doing?

1. photoreceptors are called “dark detectors” because they’re most active in the absence of light

2. In the dark, photoreceptors are depolarized which leads to the continuous release of glutamate which ****inhibits the activity of the next cells in the visual pathway, the bipolar cells.

3. Photoreceptors are actively sending an inhibitory signal to bipolar cells, preventing the transmission of visual information to the brain.

   1. This is because the visual system is designed to detect changes in light, and in the absence of light, there is no new visual information to process.

what is a chromophore?

1. Visual pigments contain a molecule called a chromophore that captures light photons and reflects color

what neurotransmitter do photoreceptors use?

1. Glutamate

what are the different types of bipolar cells?

1. Bipolar cell: A retinal cell that synapses with one or more rods or cones (not both) and with horizontal cells, and then passes the signals on to ganglion cells

   1. Diffuse bipolar cell: A bipolar cell that receives input from multiple rods

   2. Midget bipolar cell: A small bipolar cell that receives input from a single cone

what are the different types of ganglion cells?

1. Ganglion cells are the final processors of visual information in the retina

   1. P ganglion cells: Connect to the parvocellular pathway and Receive input from midget bipolar cells

   2. M ganglion cells: Connect to the magnocellular pathway and Receive input from diffuse bipolar cells

describe the horizontal pathway

1. responsible for lateral communication between photoreceptors and bipolar cells, and among themselves, which helps refine the visual signal before it is sent to the brain.

   1. Horizontal cells: These cells receive input from multiple photoreceptors and synapse onto bipolar cells. They are responsible for lateral inhibition, a process that enhances the perception of edges and contrast by inhibiting the activity of neighboring neurons.

   2. Amacrine cells: These cells receive input from bipolar cells and synapse onto ganglion cells, and also communicate with other amacrine cells and with bipolar cells. They play a role in a variety of visual functions, including motion detection, light adaptation, and the regulation of the receptive fields of ganglion cells.

2. photoreceptors —> horizontal cells —> bipolar cells —> amacrine cells —> ganglion cells

describe the vertical pathway

1. describes the flow of information from sensory receptors to higher brain areas. The retinal vertical pathway has 3 main types of neurons

   1. photoreceptors (rods and cones that transduce light energy into neural signals)

   2. bipolar cells that relay photoreceptor signals to the next level of processing

   3. ganglion cells that are the final output neurons of the retina