TEST 3 Flashcards
Organized on a similar hierarchical plan, sensory receptors, neural relays between the receptor and the neocortex, sensory coding and representation, perception
Common features of Sensory Systems
Specialized cells that convert sensory energy into neural activity, each sensory receptor responds to a narrow band of energy
Sensory receptors
Light energy, mechanical energy, air-pressure waves, chemical energy
Forms of energy that sensory receptors of different sensory systems are responsive
Ultraviolet vision, very low and very high frequency hearing, trace odor detection, seeing in dark, color vision
How sensory systems produce an idiosyncratic representation of reality for species and individuals
Specific part of the world to which a receptor cell responds
Receptive field
Each photoreceptor in the eye points in a slightly different direction and so has a unique receptive field, somatosensory receptors respond to stimulation on a very specific part of the skin
Examples of receptive fields
The brain uses information from receptive fields to ______
Identify Information
Contrast Information
Connections of receptors to cortex via intervening neurons
Neural Relays
Depending on the sensory system, three (visual and somatosensory systems) or four intervening neurons, located in the spinal cord, brainstem, and neocortex
Characteristics of Neural Relays
At each level, sensory information can be used to produce different adaptive responses.
Visual info at the level of the brainstem (superior colliculus) can produce eye movement.
Somatosensory (pain) info at the level of the spinal word can produce withdraw reflexes.
Major functional Consequences of having Neural Relays
Subjective interpretation of sensations by the brain
Perception
The context in which sensory impressions occur, emotional state, past experience
Factors that affect our sensory impressions
Light energy —> Strikes photoreceptor —> Chemical reaction —> Change in membrane potential —> Release in neurotransmitter —> Effect on nearby neurons
Initial steps in visual processing (steps from light striking the photoreceptors to the release of a neurotransmitter onto nearby neurons)
Rods and Cones are what?
Types of photoreceptors
More numerous, low levels of brightness, night vision, periphery of the retina, one light absorbing pigment, one kind
Rods
Less numerous, bright light, color vision, seeing fine detail, concentrated in the fovea, one of three light absorbing pigments, three kinds
Cones
Photoreceptors connect to retinal ganglion cells via what number of cell types?
3
Axons of the retinal ganglion cells form the ____ nerve
Optic
Rods have which retinal ganglion cell type?
M Cells
Cones have which retinal ganglion cell type?
P Cells
Left visual field information goes to the ______ hemisphere
Right
Right visual field information goes to the ____ hemisphere
Left
Nasal information crosses, temporal information does not cross
Partial Crossing at the Optic Chiasm
Projections from the retina to the lateral geniculate nucleus to the visual cortex
Geniculostriate System (pathway)
Projections from the retina to the superior colliculus to the pulvinar (thalamus) to the parietal and temporal visual areas
Tectopulvinar System (pathway)
Projections from occipital lobe, complex functions, color, form, and motion info are integrated
Features of Dorsal and Ventral Streams
The superior colliculus is found in what region of the brain?
The midbrain’s tectum
Produces orienting movements, detects and shifts the eyes toward stimuli
Functions of the tectum
The pulvinar sends ______ information to the parietal and temporal lobes
“Where”
Also called striate cortex and V1, part of the occipital cortex, layer IV. Receives input from the lateral geniculate nucleus.
Primary Visual Cortex
Also called secondary visual cortex, the remaining visual areas in the occipital cortex
Extrastriate Cortex
Color, form, and motion perception remain segregated in what?
V1 and V2
The brainstem controls what kinds of behaviors? (3)
Species typical behaviors, complex patterns of adaptive behavior, behaviors involving careful coordination
Stimulating specific regions of M1 produces movements in characteristic parts of the body
• Each motor cortex mainly controls movement on the opposite side of the body
• M1 has a partially topographic organization
• Certain areas are disproportionately large relative to the actual size of the body region (hands, fingers, lips, tongue)
• More cortical representation is associated with more precise motor control over the body region
Features of the motor cortex
• Main efferent pathways from the motor
cortex to the brainstem and spinal cord
• Axons of corticospinal tracts originate mainly in layer V pyramidal cells of the motor cortex
• Axons descend into the brainstem
• Two pathways descend from the brainstem
Features of corticospinal tracts
Anterior horn of the spinal cord
• Gray matter in the anterior portion of the spinal cord
• Contains cell bodies of neurons involved in motor function
Features of motor neurons
• The muscles on which motor neurons synapse
control body movements
• Limb muscles are arranged in pairs
• Extensors move the limb away from the trunk
• Flexors move the limb toward the trunk
•Connections between inter neurons and motor neurons of the spinal cord insure the muscles act in a complementary fashion
• The neurotransmitter at the motor-neuron-muscle junction is acetylcholine
Features of control of muscles by motor neurons
Regulate movement force
• The force with which we make movements or manipulate objects can vary over an impressive range
Functions the basal ganglia may have in movement
• Movement error correction
• The cortex sends instructions to the spinal cord
to perform a motor movement
• A copy of the same instructions is sent to the cerebellum through the inferior olive in the brainstem
• Feedback from the action is received through the spinocerebellar tract by the cerebellum
• The cerebellum has information about what you intended and what you actually did
• It can calculate the error and tell the cortex how to correct the movement
Functions the cerebellum may have in movement
• Nociception(Irritation)
• Perception of pain, temperature, and itch
• Hapsis (Pressure)
• Perception of fine touch and pressure
• Proprioception (Movement)
• Perception of body awareness, that is, body location and movement
3 types of somatosensory perception
Cells that carry somatosensory information from receptors to the spinal cord
Posterior-root ganglian neurons
Produces severe motor disability, including the
inability to learn new motor skills
Damage of posterior-root ganglion neurons
Produces inability to control movements, Movement has to be mediated by vision
Damage of proprioceptive sensory neurons
Haptic-proprioceptive axons (touch and body awareness)
• Enter spinal cord; ascend dorsally on the same side (white matter); synapse in nuclei in the base of the brain
• From the base of the brain, axons ascend the brain stem, cross, and synapse in the ventrolateral thalamus
• From the ventrolateral thalamus, most axons go to the somatosensory cortex
Features of somatosensory pathways to the brain (posterior tract)
• Nociceptive axons (pain, temperature, itch)
• Synapse with neurons in the anterior part of the spinal cord’s gray matter
• Axons from the spinal neurons cross to the anterior part of the opposite side of the spinal cord and ascend to the ventrolateral thalamus
• From the ventrolateral thalamus, some of the neurons send axons to the somatosensory cortex
Features of somatosensory pathways to the brain (anterior tract)
• Just behind the central fissure, adjacent to the primary motor cortex
• Receives projections from the thalamus
• Begins the process of constructing perceptions from somatosensory information
• Sends information to the secondary somatosensory cortex
Primary somatosensory cortex
• Located behind the primary somatosensory cortex
• Refines the construction of perceptions
• Projects to the frontal cortex
Secondary somatosensory cortex
• Composed of four representations of the body
• Each is associated with a certain class of sensory receptors
• Different “strips” of somatosensory cortex represent (from front to back)
• Muscles receptors (area 3a)
• Slow-responding skin receptors (area
3b)
• Rapidly adapting skin receptors (area 1)
• Deep tissue pressure and joint perception (area 2)
Features of somatosensory cortex
• Perceptions are constructed by
combining elementary sensations
• The construction depends on a hierarchical organization, in that basic sensations combine to form more complex sensations
Features of somatosensory cortex
• Impairs ability to make even simple discriminations and movements
• Sensory thresholds, proprioception, and hapsis
Effects of damage to the somatosensory cortex
• Does not disrupt the plans for making movements
• Disrupts how the movements are performed
• Movements are fragmented and confused
• Produces apraxia
• The inability to complete a plan of action
Effects of damage to the secondary somatosensory cortex
• Dorsal visual stream (how) projects to the secondary somatosensory cortex
• Somatosensory information is integrated with visual information to produce movements like grasping a cup
How Secondary somatosensory cortex makes a vital contribution to complex movements
