Exam 2 Flashcards
Goal of sensory systems
To shape an internal representation of the external world in a way that this internal representation facilitates the processing of/access to crucial information
Name 4 features that sensory systems extract
Modality – labelled line
Location – labelled line
Intensity – firing pattern & rate
Timing– firing pattern & rate
Modality
A property of the sensory nerve fiber.
– Receptors transduce specific type of energy into an electrical signal
– Nerve fibers activate by certain type of stimulus
– They make specific connections to structures in CNS
Location
Receptrive field of a neuron is a region of space in which the presence of a stimulus will alter the response of a neuron
Intensity
Stimulus intensity is encoded by the frequency of action potentials in sensory neurons.
– The intensity of a stimulus is also encoded by the size of the responding receptor population.
– Most of sensory systems have at least two kinds of receptros: low and high threshold receptors that contribute in encoding of the stimulus intensity.
Timing
The duration of a sensation is determined in part by the adaptation rates of receptros.
– There are two types of receptors: rapidly adapting and slowly adapting.
Rules of functional sensory and motor systems
- Each functional system involves several brain regions that carry out different type of information processing.
- Each part of the brain projects in an orderly fashion onto the next, thereby creating topographical maps.
- Identifiable pathways link the components of a functional system.
- Functional systems are hierarchically organized
- Functional systems on one side of the brain control/represent the other side of the body
Which cells form a map in primary visual cortex?
retinal ganglion cells
Where is the map from retinal ganglion cells stored in the brain?
primary visual cortex
To what features is V1 sensitive?
orientation and direction (HUBEL AND WEISEL)
Simple visual cells
Simple:
– Respond best to elongated bars or edges
– are orientation selective
– can be monocular or binocular
– have Separate ON and OFF subregions
– perform length summation
sum LGN inputs
Complex visual cells
Orientation selective
Have spatially homogeneous receptive fields (no separate ON/OFF subregions)
are nearly binocular
How is V1 organized?
In columns!
Functional Segregation of Visual Stream
Dorsal – Leads to MT
– Motion
– Depth
– Form (in V2)
Ventral – leads to V4
– Color
– Form
Depth (in V2)
Perception of Depth depends on what?
Depth vision depends on monocular cues and binocular disparity
Relative Size
objects that are closer appear larger, while objects that are distant appear smaller
Relative motion
apparent slowness indicates an object is distant
interposition
closer objects partially obstruct the view of more distant objects
Relative height
distant objects appear higher in your field of vision than close objects do
Texture gradient
distant objects usually have a much smoother texture than nearby objects
Relative clarity
distant objects are less clear than nearby objects
Linear perspective
parallel lines appear to converge in the distance
Monocular cues for depth perception
familiar size
occlusion
distribution of shadows/illumination
motion
linear perspective
size perspective
binocular depth cues
used by both eyes
Convergence:
– muscle tension in the eyes increases as objects move closer
Retinal Disparity:
– each eye has a slightly different perspective and image than the other