Introduction to Perception

Question 1

Sensation: definition

Answer 1

Awareness do to the stimulation of a sense organ

Question 2

Sensation

What are the three components of sensory systems? Which ones do we know the most about

Answer 2

Receptors: these are the sense organs. This is where sensation starts and this is what we know the most about

Pathways

Target areas

Question 3

What are the three common features of the various sensory modalities?

Answer 3

1. A physical stimulus
2. Transformation of the stimulus into neuronal signals (the stimulus has to be transformed into a signal so that we can PERCEIVE it.
3. A response to the signals in the form of a perception or a conscious experience of sensation

Question 4

Perception: definition

Answer 4

An internal construction of the external world according to the CNS; the conscious experience of sensation

Question 5

Perception

What is the distinction between the stimulus and perception?

Answer 5

Our perceptions of colors, tomes, smells, and tastes are mental creations constructed by the brain in response to the sensory experience. They do not exist as such outside the brain.

Question 6

Coding Sensory Information

What is a neural Code?

Answer 6

It describes the relationship between the activity in a specified neural population and its functional consequences.

Question 7

Coding Sensory Information

What are the 4 attributes of stimuli that all sensory systems encode?

Answer 7

Modality
Location
Intensity
Timing/Duration

Question 8

Coding Sensory Information: Modality

Definition

Answer 8

Defines the general class of stimulus

It is determined by the stimulus energy (the sensory stimulus) and the receptors specialized to sense that energy

Question 9

Coding Sensory Information: Modality

What is the labeled line code?

Answer 9

The coding mechanism for a stimulus modality

Receptors respond to specific stimuli, and pathways carrying sensory information centrally are therefore also specific, forming a “labelled line” regarding a particular stimulus

Question 10

Coding Sensory Information: Modality

What is the rose of the sensory receptors?

Answer 10

The are the first cell (or region of a cell) in each sensory pathway; they are morphologically specialized to transform stimulus energy into electrical energy.

Question 11

Coding Sensory Information: Modality

How are sensory receptors classified?

Answer 11

Based on the type of stimulus energy to which they are most sensitive.

Question 12

Coding Sensory Information: Modality

What are the properties of sensory receptors?

Answer 12

Each receptor responds to a narrow range of stimulus energy.

Receptors transduce stimulus energy into electrical signals (receptor potentials)

Question 13

Coding Sensory Information: Modality

What are mechanisms used by sensory receptors to transduce stimulus energy into a signal? What are they similar to?

Answer 13

Mechanisms are similar to those used by the receptors at chemical synapses. Thy can be

Ionotropic receptors: These are present in the somatosensory, Viscerosensory, Auditory, Vestibular, and Gustatory systems; these directly open ion channels and mediate fast transmission

Metabotropic Receptors: These are present tin the somatosensory, visual, olfactory, and gustatory systems; indirectly associated with ion channels via g-proteins and second messengers; mediate slower transmission

Question 14

Coding Sensory Information: Location

How do receptors code for location of a stimulus (visual and somatosensory systems)

Answer 14

Spatial arrangement of the activated receptors conveys information about the location of the stimulus on the body (somatosensory) or in space (visual); location is determined by the receptive fields of the sensory neurons that are being activated.

Question 15

Coding Sensory Information: Location

What aspects of the stimulus are encompassed by the location?

Answer 15

Discrimination in the size and shape of an object.

Resolution of the fine detail of a stimulus.

Question 16

Coding Sensory Information: Location

What is the role or receptor density?

Answer 16

The density of receptors in a given area determines how well the sensory system can resolve the detail in the stimuli in that area.

Question 17

Coding Sensory Information: Location

What is the relationship between receptor density and the size of the receptive fields and spatial resolution?

Answer 17

The higher the density of the receptors, the smaller the receptive fields, and the finer the spatial resolution.

These differences are represented by topographical maps in the CNS (like homunculus)

Question 18

Coding Sensory Information: Location

What is the role of the spatial arrangement of the receptors in the Auditory, Vestibular, Olfactory, and Gustatory systems?

Answer 18

The spatial organization of the receptors in these modalities represents the energy spectrum of each modality rather than information about the location of the stimuli on the body or in space.

Question 19

Coding Sensory Information: Intensity

What determines the intensity of the signal?

Answer 19

Amplitude of the receptor potential (these are at the INPUT part of the neuron and are graded, local potentials)

Total number of active sensory neurons

Question 20

Coding Sensory Information: Intensity

What is the stimulus threshold?

Answer 20

The lowest stimulus amplitude that can be detected - the least amount of receptor potential that needs to signal the neuron to set off an action potential.

Different receptors have different stimulus thresholds

Question 21

Coding Sensory Information: Intensity

How is intensity represented in the signal?

Answer 21

Represented by the FREQUENCY of action potentials (frequency code) and the NUMBER of activated receptors (population code) of sensory neurons.

Question 22

Coding Sensory Information: Timing/Duration

What determines the timing or duration of the signal?

Answer 22

Changes in the PATTERN of sensory neuron activity.

Question 23

Coding Sensory Information: Timing/Duration

Do receptors adapt to constant stimulation? How?

Answer 23

Yes. They can adapt either rapidly or slowly but the mechanism for this is not well understood.

Question 24

Coding Sensory Information: Timing/Duration

Rapidly Adapting Receptors - when do they respond? what do they signal?

Answer 24

Respond only at the beginning and end of a stimulus.

Signal the rate at which the stimulus is applied or removed.

Question 25

Coding Sensory Information: Timing/Duration

Slowly Adapting Receptors - when do they respond? what do they signal?

Answer 25

Respond to prolonged and constant stimulation

signal the stimulus magnitude for minutes. Initially the frequency is high and then it evens out.

Question 26

Coding Sensory Information: Timing/Duration

How is the timing or duration of a stimulus represented by the signal?

Answer 26

By the changes in FREQUENCY of action potentials of sensory neurons.

Question 27

Common Plan of Sensory Systems:

How is information conveyed when different populations of sensory neurons are simultaneously activated?

Answer 27

In parallel pathways, meaning that information about various submodalities can be carried to the CNS via different pathways at the same time.

Specific submodalites depend upon the combined activity of populations of receptors sensitive to overlapping energy ranges.

Question 28

Common Plan of Sensory Systems:

How is information processed as it moves from the periphery to the CNS?

Answer 28

information is processed in a series of relay nuclei.

information goes from the population or receptors to the 2nd order neurons in the spinal cord, medulla, etc, to the higher order/1st order neurons.

At each level, signals are integrated into more complex sensory information

The sequence of connections gives rise to a distinct functional hierarchy.

Question 29

Common Plan of Sensory Systems:

What is the difference between the receptor fields of 1st and 2nd order neurons and why?

Answer 29

Each 2nd order receptor receives information from a population of receptors and therefore has a bigger and more complex receptive field than any of the 1st order neurons.

Question 30

Common Plan of Sensory Systems:

What is the role of inhibitory interneurons within the relay nuclei?

Answer 30

They they produce inhibitory regions within the receptive fields of the higher order neurons.

these inhibitory regions enhance the contrast between stimuli, thereby improving the resolution of spacial detail