Chapter 7 - BioPsychology - Mechanisms of Perception

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Primary Sensory Cortex

The area of sensory cortex that receives most of its input directly from the thalamic relay nuclei of that system

Secondary Sensory Cortex

Comprises the areas of the sensory cortex that receive most of their input from the primary sensory cortex of that system or from other areas of secondary sensory cortex of the same system

Association cortex

● Is any area of cortex that receives input from more than one sensory system.

● Most input to areas of association cortex comes via areas of the secondary sensory cortex.

hierarchical organization

functional segregation

parallel processing

Sensory structures are characterized by three major principles:

Hierarchical organization

A hierarchy is a system whose members can be assigned to specific levels or ranks in relation to one another.

Functional segregation

Characterizes the organization of sensory systems.

Each of the three levels of cerebral cortex—primary, secondary, and association—in each sensory system contains functionally distinct areas that specialize in different kinds of analysis.

Parallel processing

The simultaneous analysis of a signal in different ways by the multiple parallel pathways of a neural network.

True

True or False:

two fundamentally same kinds of parallel streams of analysis in our sensory systems:

■ one capable of influencing our behavior without our conscious awareness

■ one that influences our behavior by engaging our conscious awareness.

PROSOPAGNOSIA

- A MAN MISTOOK HIS WIFE FOR A HAT- A man who had visual agnosia, specifically ______________

AUDITORY SYSTEM

● The function of the _____________ is the perception of sound.

Sounds

are vibrations of air molecules that stimulate the auditory system

True

True or False:

humans hear only those molecular vibrations between about 20 and 20,000 hertz

perceptions of loudness, pitch, and timbre

The amplitude, frequency, and complexity of the molecular vibrations are most closely linked to _________, ____________, and ____________

Pure tones (sine wave vibrations)

● exist only in laboratories and sound recording studios;

● in real life, sound is always associated with complex patterns of vibrations.

Sound waves

travel from the outer ear down the auditory canal and cause the tympanic membrane (the eardrum) to vibrate.

the malleus (the hammer), the incus (the anvil), and the stapes (the stirrup)

the small bones of the middle ear:

oval window

The vibrations of the stapes trigger vibrations of the membrane called the _________, which in turn transfers the vibrations to the fluid of the snail-shaped cochlea.

kokhlos

it means “land snail”

Cochlea

is a long, coiled tube with an internal structure running almost to its tip.

The organ of corti

This internal structure is the auditory receptor organ

True

True or False:

Humans can hear differences in pure tones that differ in frequency by only 0.2 percent.

True

True or False:

The major principle of cochlear coding is that different frequencies produce maximal stimulation of hair cells at different points along the basilar membrane

True

True or False:

higher frequencies producing greater activation closer to the windows

True

True or False:

lower frequencies producing greater activation at the tip of the basilar membrane

tonotopic

The organization of the auditory system is largely _________

True

True or False:

There is no major auditory pathway to the cortex comparable to the visual system’s retina-geniculate-striate pathway.

Instead, there is a network of auditory pathways

the ipsilateral cochlear nuclei

Where do the axons of each auditory nerve synapse?

from which many projections lead to the superior olives on both sides of the brain stem at the same level

axons of the olivary neurons

What axons project via the lateral lemniscus to the inferior colliculi?

where they synapse on neurons that project to the medial geniculate nuclei of the thalamus, which in turn project to the primary auditory cortex

the primary auditory cortex

In primates, _________, which receives the majority of its input from the medial geniculate nucleus, is located in the temporal lobe, hidden from view within the lateral fissure).

the core region

Primate primary auditory cortex comprises three adjacent areas.

Together these three areas are referred to as _______

band—often called the belt

It surrounds the core region of areas of secondary auditory cortex.

parabelt areas

Areas of secondary auditory cortex outside the belt are called ________

20

How many separate areas of auditory cortex are in primates?

Anterior auditory pathway

a pathway that is more involved in identifying sounds (what)

Posterior auditory pathway

a pathway that is more involved in locating sounds (where)

lateral fissure

Efforts to characterize the effects of damage to human auditory cortex have been complicated by the fact that most human auditory cortex is in the _______.

Consequently, it is rarely destroyed in its entirety; and if it is, there is almost always extensive damage to surrounding tissue

True

True or False

efforts to understand the effects of auditory cortex damage have relied largely on the study of surgically placed lesions in nonhumans

True

True or False

Most studies of the effects of auditory cortex lesions have assessed the effects of large lesions that involve the core region and most of the belt and parabelt areas.

the subcortical circuits

Given the large size of the lesions in most studies, the lack of severe permanent deficits is surprising, suggesting that ___________ serve more complex and important auditory functions than was once assumed.

Somatosensations

- sensations from your body

Somatosensory system

- mediates these bodily sensations.

Exteroceptive system

○ Main focus of this chapter.

○ Senses external stimulus applied to the skin.

○ Has three divisions for:

■ Mechanical stimuli

■ Thermal stimuli

■ Nociceptive stimuli

■ Mechanical stimuli

touch

■ Thermal stimuli

temp

■ Nociceptive stimuli

pain

Proprioceptive stimuli

○ Monitors information about the position of the body that comes from receptors in the muscles, joints and organs of balance

Interoceptive system

○ provides general information about conditions within the body (e.g., temperature and blood pressure)

FREE NERVE ENDINGS

○ simplest cutaneous receptors.

○ neuron endings with no specialized structures on them.

○ particularly sensitive to temperature change and pain

PACINIAN CORPUSCLES

○ largest and deepest cutaneous receptors.

○ Onionlike in appearance.

○ they adapt rapidly, they respond to sudden displacements of the skin but not to constant pressure.

MERKEL DISKS

○ Adopt slowly.

○ Respond to gradual skin indentation.

RUFFINI ENDINGS

○ Adapt slowly.

○ Respond to skin stretch.

True

True or False:

The pressure on the skin evokes a burst of firing in all receptors which corresponds to the sensation of being touched. After a few hundred milliseconds, only the slowly adapting receptors remain active. The quality of the sensation changes. As a result, you are often totally unaware of constant skin pressure unless you focus your attention on it.

stereognosis

As a consequence, when you try to identify objects by touch (_________), you manipulate them in your hands so that the pattern of stimulation continually changes.

True

True or False:

Having some receptors that adapt quickly and some that adapt slowly provides information about both the dynamic and static qualities of tactual stimuli.

Stimuli

this is applied to the skin and it deforms or changes the chemistry of the receptor, and this in turn changes the permeability of the receptor cell membrane to various ions.

neural signal

This is the result after the changes in the permeability of the receptor cell membrane to various ions

skin cells that surround particular receptors

they also seem to play a role in the quality of the sensations produced by that receptor.

new forms of tactile sensation are still being discovered

neural fibers

the ____ that carry information from cutaneous receptors and other somatosensory receptors gather together in nerves and enter the spinal cord via the dorsal roots.

dorsal roots

The neural fibers that carry information from cutaneous receptors and other somatosensory receptors gather together in nerves and enter the spinal cord via the _______.

DERMATOME

- The neural fibers that carry information from cutaneous receptors and other somatosensory receptors gather together in nerves and enter the spinal cord.

False - little

True or False:

Because there is considerable overlap between adjacent dermatomes, destruction of a single dorsal root typically produces more somatosensory loss

DORSAL-COLUM MEDIAL-LEMNISCUS SYSTEM

ANTEROLATERAL SYSTEM

TWO MAJOR SOMATOSENSORY PATHWAYS

DORSAL-COLUMN MEDIAL-LEMNISCUS SYSTEM

○ Carry information about touch and proprioception

dorsal root; dorsal column

Sensory neurons enter via _____.

Ascend ipsilaterally in the ______ .

True

True or False:

Axons from the dorsal column decussate

True

True or False:

DORSAL-COLUM MEDIAL-LEMNISCUS SYSTEM have the following as part of the somatosensory pathway

➢ Ascend in the medial lemniscus to the ventral posterior nucleus of the thalamus.

➢ Ventral posterior nuclei recieve input.

➢ Carry information to the somatosensory cortex.

ANTEROLATERAL SYSTEM

○ Carry information about pain and temperature.

Dorsal

_____ roots neurons synapse as they enter the spinal cord

second-order neurons

Axons of _______ decussate and then ascent to the brain contralateral anterolateral of the spinal cord.

spinothalamic tract, spinoreticular tract, and spinotectal tract.

The Anterolateral System contain:

Trigeminal nerves

______ carry information from the face to the same thalamic sites.

Information reaches the thalamus.

Distributed to the somatosensory cortex and other parts of the brain

False - ascending

True or False:

If both descending somatosensory paths are completely transected by a spinal injury, the patient can feel no body sensation from below the level of the cut.

Penfield and his colleagues

In 1937, they (_________) mapped the primary somatosensory cortex of patients during neurosurgery.

Penfield

He applied electrical stimulation to various sites on the cortical surface, and the patients, under a local anesthetic, described what they felt.

When stimulation was applied to the postcentral gyrus, the patients reported somatosensory sensations in various parts of the body.

He discovered that the human primary somatosensory cortex (SI) is somatotopic — organized according to a map of the body surface

Penfield

He created the somatotopic map or the somatosensory homunculus.

“little man”

other meaning for somatosensory homunculus

True

True or False:

greatest proportion of SI is dedicated to receiving input from the parts of the body we use to make tactile discriminations (e.g., hands, lips, and tongue).

True

True or False:

only small areas of SI receive input from large areas of the body(e.g., back) that are not usually used to make somatosensory discriminations

The secondary somatosensory cortex (SII)

It receives most of its input from SI, and receives substantial input from both sides of the body.

posterior parietal lobe

Much of the output of SI and SII goes to the association cortex of the _________.

Columnar organization

• Each neuron in a particular column of primary somatosensory cortex had a receptive field on the same part of the body and responded most robustly to the same type of tactile stimuli (e.g., light touch or heat).

• Each neuron in a particular column of primary somatosensory cortex had a receptive field on the same part of the body and responded most robustly to the same type of tactile stimuli (e.g., light touch or heat).

dorsal stream

ventral stream

TWO STREAMS OF ANALYSIS

dorsal stream

a _________ that projects to posterior parietal cortex and participates in multisensory integration and direction of attention

ventral stream

a ________ that projects to SII and participates in the perception of objects’ shapes

True

true or False:

the effects of damage to the primary somatosensory cortex are often remarkably mild because it features numerous parallel pathways.

Corkin, Milner, and Rasmussen (1970)

they assessed the somatosensory abilities of epileptic patients before and after a unilateral excision that included SI

The patients displayed two minor contralateral deficits:

○ A reduced ability to detect light touch.

○ A reduced ability to identify objects by touch.

Somatosensory signals

these are conducted to the highest level of the sensory hierarchy, to areas of association cortex in prefrontal and posterior parietal cortex.

Bimodal neurons

○ neurons that respond to both somatosensory and visual stimuli.

False - left

True or False:

if a neuron has a somatosensory receptive field centered in the left hand, its visual field is adjacent to the left hand. As the right hand moves, the visual receptive field of the neuron moves with it.

The case of W.M., who reduced his scotoma with his hand.

● Suffered a stroke in his right posterior cerebral artery that affected a large area of right occipital and parietal lobe.

● Diagnosed with severe left hemianopsia (a condition in which a scotoma covers half the visual field).

● When he was tested with his left hand extended into his left visual field, his ability to detect stimuli in his left visual field improved significantly.

ASTEREOGNOSIA

ASOMATOGNOSIA

ANOSOGNOSIA

CONTRALATERAL NEGLECT

SOMATOSENSORY AGNOSIA (4)

Astereognosia

○ inability to recognize objects by touch.

○ Pure astereognosia is rare, it is often simple sensory deficits.

Asomatognosia

○ failure to recognize parts of one’s own body.

○ usually unilateral, affecting only the left side of the body.

○ with extensive damage to the right temporal and posterior parietal lobe.

ANOSOGNOSIA

○ failure of neuropsychological patients to recognize their own symptoms.

○ asomatognosia is often accompanied by this.

○ is a common symptom of many neurological disorders.

CONTRALATERAL NEGLECT

○ tendency not to respond to stimuli that are contralateral to a right-hemisphere injury.

○ Asomatognosia is commonly a component of this

The case of Aunt Betty

● Suffered from left hemiplegia (left-side paralysis), following a right-hemisphere stroke.

● Couldn’t see out of her left eye, and recognize body parts from the left side of her body.

● Diagnosed with asomatognosia, anosognosia, and contralateral neglect.

RUBBER- ILLUSION

● the feeling that an extraneous object, in this case a rubber hand, is actually part of one’s own body).

functional imaging studies

these have suggested that association cortex in the posterior parietal and frontal lobes plays a role in its induction.

True

True or False:

It has been suggested that those frontal and parietal bimodal neurons with both visual and somatosensory fields play a critical role.

perception of pain

it is paradoxical in three aspects.