6. From Signals to Sensations

Question 1

What do the senses convey specific information about?

Answer 1

Some source of physical energy

Question 2

Each what has a ‘labelled line’ which means high level specificity?

Answer 2

Each sensory modality

Question 3

Which receptor can only convey info to the brain when the skin is stretched?

Answer 3

The Pacinian Corpuscle

Question 4

Each time you stretch your skin, what happens to the membrane?

Answer 4

It moves and opens the ion channels and triggers an AP

Question 5

List 3 things that each sensory modality responds to/has

Answer 5

1. Responds to a range of stimuli
2. Has evolved to fit the animal’s need
3. Has a specific set of codes

Question 6

Sensory receptor organs act as filters of the environment to detect and respond to what?

Answer 6

Specific events

Question 7

Sensory receptor organs are known as the gate between what?

Answer 7

The external environment and the brain

Question 8

Define stimulus

Answer 8

Event that affects the sensory organ

Question 9

Describe the task that sensory systems complete

Answer 9

They convert environmental signals into neural activity that can influence the motor system of the animal

Question 10

What are the 3 methods of studying sensory processing?

Answer 10

1. Psychophysics
2. Electrophysiological
3. Neuroimaging

Question 11

Describe psychophysics

Answer 11

Use behavioural testing to establish the sensitivity of a sensory system and the ‘rules’ of its operation

Question 12

Describe electrophysiological

Answer 12

Recording from single neurons or small groups of neurons along the sensory pathway to find out how the neural circuitry gives rise to the perceptual abilities

Question 13

Describe neuroimaging

Answer 13

In humans that are doing perceptual tasks to identify the brain areas responsible

Question 14

Describe qualitative features of sensory signals and what it is often referred to

Answer 14

Feature such as colour or odourant (often referred to as modality)

Question 15

Describe quantitative features of the sensory signal and what it is often referred to

Answer 15

Features such as magnitude (often referred to as the intensity)

Question 16

What is a common strategy of sensory systems?

Answer 16

Separate neural pathways specialised for estimating different types of stimulus features

Question 17

What are the 2 main functions of each sensory system?

Answer 17

Detection and discrimination

Question 18

Define detection

Answer 18

The detection of a signal (i.e. is the signal present)

Question 19

Define discrimination

Answer 19

Discrimination of some aspects of a sensory input (often referred to as estimation) (i.e. is this strong)

Question 20

Define adequate stimulus

Answer 20

Type of stimulus for which a given sensory organ is particularly adapted (essential because each organ can only detect specific stimuli)

Question 21

Define transducer function of receptors

Answer 21

The process in which a stimulus energy is transducer into an electrical response

Question 22

What type of cells does sensory processing start with?

Answer 22

Receptor cells

Question 23

Upon exposure to a stimulus, a receptor cells can convert energy into a…

Answer 23

Change in electrical potential across its membrane

Question 24

Define sensory transduction

Answer 24

Changing physical energy to electrical potentials/neural activity - when the ion channels open

Question 25

The structure of the receptor determines what?

Answer 25

The form of energy to which it will respond

Question 26

Describe receptor potential

Answer 26

Step between the arrival of energy at receptor cell and the initiation of an AP The AP goes through the pathway and to the brain

Question 27

Describe the 4 stages of an excitatory event (specifically in the Pacinian Corpuscle)

Answer 27

1. Mechanical stimulation deforms the corpuscle 2. Deformation of the corpuscle stretches the tip of the axon 3. Stretching the axon opens mechanically gated ion channels in the membrane, allowing sodium ions to enter 4. When the receptor reaches the threshold amplitude, the axon produces an AP

Question 28

What are the 4 stages of sensory receptors

Answer 28

1. Sensory transduction 2. Amplification 3. Transmission 4. Integration

Question 29

Describe the process of sensory transduction in a sensory receptor

Answer 29

They traduce (transform/translate) the physical energy of a stimulus into a change in the membrane potential

Question 30

Outline the process of amplification by a sensory receptor

Answer 30

The sensory receptor will strengthen the energy of the stimulus

Question 31

Outline the process of transmission by a sensory receptor

Answer 31

AP's from receptors, or from neurons connected to receptors, reach the CNS - the encoding of the signal

Question 32

Outline the process of integration by a sensory receptor

Answer 32

Receptors contribute to the processing of a signal e.g. many receptors show sensory adaptation such as, not being able to feel clothing

Question 33

What are the 4 attributes of the stimulus?

Answer 33

Modality Intensity Location Duration

Question 34

The most basic mechanism for identifying the nature of a sensory input is via what?

Answer 34

Labelled lines

Question 35

Define somatosensory system

Answer 35

Receptor is a specialised peripheral element that is associated with the peripheral process of a sensory neuron

Question 36

Outline auditory and visual systems

Answer 36

A distance type of receptor cell is present. In the auditory system, the receptor synapses directly on the ganglion cell, whereas in the visual system, an interneuron receives synapses from the photoreceptor and in turn synapses on the retinal ganglion cell

Question 37

How is the brain able to recognise the different sensations as separate and distinct?

Answer 37

Because each sensory modality sends its APs along separate nerve tracts

Question 38

Define labelled lines

Answer 38

Particular neurons are at the outset labelled for distinctive sensory experience (fast, parallel processing)

Question 39

The estimated intensity of a stimulus is _ _ __ __ of the actual intensity

Answer 39

Not a linear function

Question 40

Increases of a weak signal generate a ___ perceived increase than increases of a strong signal

Answer 40

Larger

Question 41

Which best describes the relationship between stimulus strength and perceived stimulus intensity, logarithmic or power law?

Answer 41

A power law

Question 42

How many neurons does it take to code for stimulus intensity and how does it do this?

Answer 42

A single neuron by increasing the frequency of APs

Question 43

As the strength of the stimulus increases, what happens in terms of the neurons?

Answer 43

More neurons are recruited as intensity increases

Question 44

Define range fractionation

Answer 44

Different receptors are specialist in particular segment (fractions) of an intensity scale

Question 45

What does the receptive field of a sensory neurone consist of?

Answer 45

A region of space in which a stimulus will alter the neurone firing rate

Question 46

The receptor of each primary neurone can pick up information from where?

Answer 46

A specific area (receptive field)

Question 47

If you touch the area around the centre then what will occur?

Answer 47

An AP will occur (EPSP)

Question 48

If you touch the surrounding area, will there be an AP?

Answer 48

No

Question 49

Smaller receptive fields =

Answer 49

Greater acuity

Question 50

What does lateral inhibition allow us to see?

Answer 50

Specificity in touch in the skin

Question 51

The brain can code how many different events at the same time? and what is this due to?

Answer 51

2 due to lateral inhibition between

Question 52

Outline sensory adaptation

Answer 52

Many receptors showing progressive loss of response when stimulation is maintained

Question 53

What do tonic receptors produce? (and give an example)

Answer 53

Constant rate of firing as long as the stimulus is applied (e.g. pain)

Question 54

Outline how phasic receptors respond to stimuli

Answer 54

They have a burst of activity but quickly reduce firing rate if the stimulus is maintained

Question 55

What other way can we suppress receptors? (other than sensory adaptation)

Answer 55

Top down processing which can change the intensity of perceived signal

Question 56

Sensory info will reach which cortical area?

Answer 56

The thalamus which sends signals to the cortex

Question 57

Which sense is the only one whereby the sensory information does not go via the thalamus?

Answer 57

Smell

Question 58

Sensory information enters the CNS through the ___ or the ___

Answer 58

Brainstem or spinal cord

Question 59

Where do signals of two sensory modalities converge?

Answer 59

On a bimodal neuron

Question 60

What does synesthesia result from?

Answer 60

'Cross-wiring' in the brain