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per neuro > Somatosensory System > Flashcards

Somatosensory System Flashcards

1
Q

what can we do through touch?

A

shape perception; the properties of the surfaces of objects, texture perception…both are important parts of the tactile system

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2
Q

what do we do when we’re not highly familiar with an object?

A

have to explore the object through touch to skin. we get a lot of info from tactile and visual information about the object’s texture and surface. touching the object is more sensitive and gives a broader array of info.

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3
Q

what is texture information, and its relation to taste?

A

it is an important component in our ability to enjoy and perceive the contents of food. the taste and olfactory system give the perception of flavour, as taste is a multisensory percept.

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4
Q

what converts tactile information from the tongue?

A

the trigeminal nerve in the jaw converts tactile information from the tongue to the brain.
it is very sensitive to shape and texture.
we can communicate information about shapes to blinded individuals through the tongue.
the tongue is a sensory substitution device in those who cannot see.

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5
Q

blinded individuals and touch?

A

the tongue can convert tactile information to brain and is is a sensory substitution device in those who cannot see..
if you stimulate the back with a shape, blind people can learn to recognise objects when vision is deprived.

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6
Q

visual system and force?

A

visual system needs to know whereI will pick up object if full of liquid, what is the appropriate force I have to use?
babies lack this ability and use the wrong force. overtime they will learn what is the most appropriate action. tactile bit is knowing what type of force is needed, the shape, the texture… all important info that we need.

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7
Q

how are the 4 mechanoreceptors defined?

A
  • by how deeply embedded they are in the skin, or depth in skin/ location in skin layers
  • their function, in how they respond to different stimulation. their function is also their receptive field and adaptive properties
  • their unique morphology/ structure
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8
Q

what do mechanoreceptors require?

A

they require physical force in order to respond to stimulation, causing membrane deep polarisation and action potentials are fired.

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9
Q

what are the types of mechanoreceptors?

A
  1. Meissner’s Corpuscles
  2. Pacinian Corpuscles
  3. Ruffini nerve endings
  4. Merkel’s Disks
  5. free nerve endings
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10
Q

what is glabrous skin?

A

an epidermal covering that is totally or relatively devoid of hairs

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11
Q

where are we most sensitive to touch in glabrous regions of skin?

A

touch in lips, palms of hands and soles of feet= glabrous.

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12
Q

why are the soles of feet important to study?

A

we feel force on the soles of our feet.
this force sends a signal to the brain about how to balance our body to maintain posture.
wearing heels changes the force, the brain counts for this and readjusts balance.
therefore, soles of feet are NB source of information.
studying the sensitivity of soles on feet may explain why older adults fall with no environmental hazards.

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13
Q

what is the rate at which mechanoreceptors transmit information? rate at which mechano’s recover from transmitting info?

A

mechanoreceptors either recover very quickly or very slowly.

- fast/slow adapting = F/S adapting

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14
Q

why might we encode information in bursts of energy vs. mechanoreceptors continually sending info to the brain?

A

when (haptically)exploring an object=sending continuous tactile info to the brain, slowly adapting mechanoreceptors as brain receives constant info.

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15
Q

what do the mechanoreceptors do?

A

the 4 types of cutaneous mechanoreceptors work in harmony with eachother to send: the right type of information, and the most information they can to the brain.

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16
Q

receptive field size and mechanoreceptors?

A
  • if the mechano’ is responding to a tiny piece of skin it means it’s not very detailed.
  • if the mechano’ is responding to a large piece of skin then it is not exactly sharp.
    …small r.f.= mechano’s being very precise:
  • meissner’s corpuscles are F/A and are very precise in what it reports to the brain
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17
Q

what are the receptive field sizes of the mechanoreceptors?

A
  • Fast/A and small field size= Meissner’s corpuscles
  • Fast/A and large field size= Pacinian corpuscle
  • Slow/A and small field size= Merkel’s disks
  • Fast/A and large field size= Ruffini Ending
    ….field size and F/S adapting=receptive field
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18
Q

what do cutaneous mechanoreceptors in the hand respond to?

A

meissner’s corpuscles: pressure/slow pushing
merkel’s disks: flutter
pacinian corpuscles: rapid vibration
ruffini endings: stretching

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19
Q

what is the temporal acuity of the skin?

A
  • must be 5.5ms apart to clearly decipher which event happened first, or decide if 2 separate events
  • successiveness= 2 stimuli separated by 5.5ms and perceived as 2 at a single locus
  • temporal order=2 successive stimuli at separate sites separated by 20ms and determine which site was first
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20
Q

individual differences and temporal acuity of the skin?

A

ID’s depend on whether use hands a lot

the threshold becomes lighter if you burnt yourself

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21
Q

what is spatial acuity?

A

how small something can be for us to perceive it

more accurate with vision

22
Q

what is temporal variation?

A

how much spatial acuity is affected by visual information

23
Q

where is the 2-point discrimination threshold high and low on body (2PDT)?

A

2PDT is low at finger tips and lips

2PDT is high on back

24
Q

what did Penfield and Rasmussen claim in 1950?

A

the psychophysical threshold relates directly to the cortical representation.
lower thresholds=greater tactile sensitivity, as greater cortical regions are more sensitive to touch

25
Q

tactile processing in the somatosensory cortex

A

information is transmitted to the cortex from the skin via the dorsal columnal ‘lemniscal’ pathway

    • skin- cureate nucleus (CN) in medulla…somatosensory neurons in CN project to the ventro posterior lateral nuclei (VPL) in thalamus
    • from thalamus - S1/ primary somatosensory cortex - Brodmann Areas
26
Q

what are the Brodmann areas in the S1?

A

Brodmann areas: 3a, 3b, 1+2

  • 3a: proprioception/ information from muscles about where they are in space
  • 3b: cutaneous stimulation in 1+2 receive inputs from 3b
  • after information is processed in S1 perception happens and then is routed to association areas.
27
Q

what did Kalaska in 1983 say?

A

that information is then routed to association areas such as the posterior parietal cortex (PPC)

28
Q

what did Friedman in 1986 say?

A

that information is then routed to association areas such as the secondary somatosensory cortex/ S2

29
Q

columnar organisation of S1?

A
  • reminiscent of the visual system
  • info from F/S adapting mechanoreceptors are organised in columns, each digit has collumnary organisation
  • not sure of when the integration of info occurs
30
Q

what are spatial event plots?

A

spatial event plots/ SEP’s measure the tactile sensitivity of mechanoreceptors

31
Q

tactile modality maps in S1

A

Pressure, or skin indentation, flutter, vibration= psychophysically distinct tactile information from the stimulation of different mechanoreceptors, due to their location/depth in skin and their function.
- these psychophysically distinct tactile information are produced by frequency specific vibrotactile stimulation in skin

32
Q

what did Friedman in 2004 do?

A

tested in primates
information remains separate up until input stage when different patches of neurons are activated, such as area 3b in S1
…evidence for function of 3b was to respond to pressure/flutter/ vibratory stimulation

33
Q

orientation perception?

A

passive presentation of different orientation of edges to finger tip, we have the ability to discriminate between different orientations, we are very accurate at this
the tuning of the somatosensory cortex is very precise, neurons selectively tuned to different types of orientation
it doesn’t matter if stimulation is indented onto skin or if animal ‘stands’ on stimulation.

34
Q

are we sensitive to deviations from vertical and horizontal lines?

A

cardinal points of vertical and horizontal lines are overrepresented in in visual and tactile systems, more neurons means higher sensitivity
we are very sensitive to deviations from horizontal and vertical lines, not so much when line is oblique.

35
Q

what did Bensmaia in 2008 say?

A

if you were born in a rural environment, has a direct effect on perceptual abilities
there is a slight bias towards counter-clockwise orientation

36
Q

secondary somatosensory system/ SII

A

SII forms part of the parietal operculum
it is somatotopically organised
it receives input from S1 and thalamus
bilateral representation of the body

37
Q

posterior parietal cortex (PPC)?

A

has a role in high-level sensory processing

involved in tactile object recognition

38
Q

how the familiarity of objects and information about object parts are processed in brain?

A
  • the ability to represent ownership over ones body starts with the somatosensory cortex
  • awareness of objects and to make decisions about the familiarity of the object, converges information about the parts of the object occurs in the PPC…integration of info results in a rich representation of the object under exploration in the PPC
39
Q

what is haptic shape perception?

A

haptic shape perception distinguishes between passive tactile stimulation, whereas haptic=active exploration of objects

40
Q

how is shape information available?

A

shape information is available at multiple scales: local and global.
local=2D patterns, Braille letters
global=3D objects

41
Q

are there challenges in how the brain perceives shape through touch with hands?

A

1) exploration: mechanoreceptors moving with skin, holding the object stimulates multiple regions of the hand. at each site there are different tactile information, yet we perceive a whole object despite perceiving info across hand.
2) what are the cues used to understand that the object is a single object? unique force. if different features are similar it is likely that they all belong to the same object. principles of info processing fit in with Gestalt’s laws of grouping.

42
Q

what does haptic shape perception involve?

A

haptic shape perception involved the integration of information from: proprioception (where is the hand and how is it configured?) + tactile (cutaneous signals stimulated by contact with object).

43
Q

how do we perceive a single coherent object?

A

receptive fields from the neurons in S2:

  • info is integrated across different stimulated sites on skin
  • geometric structure is detected and grouped together (edges), Fitzgerald 2006.
44
Q

what did Amedi in Neuroscience, 2001 say?

A

LOTV/ lateral occipital tactile-visual…activated by feeling objects and not seeing them

45
Q

where is the location of objects processed?

A

right-parieto-occipital cortex

46
Q

what did Reed in 1996 state?

A

that damage to the right-parieto-occipital cortex (parietal damage) resulted in tactile agnosia.

47
Q

where is the shape of the object processed?

A

lateral occipital complex (LOC)

- visual and haptic recognition

48
Q

who are Leederman and Klatsky?

A

leederman and klatsky are the leaders in object recognition through touch field.
they say that there are optimal ways of exploring objects through different hand movements, dependant on the area of object that you are exploring
-enclosure infers size
-contour following infers shape

49
Q

what did leederman and klatsky do?

A

they predicted the optimal perception of performance through matching exploratory procedure with the property pf the object you wish to perceive.
…lateral motion gives the best performance in perceiving texture.

50
Q

receptive field size and cortical neurons in S1

A

the smaller the rf is, the greater sensory sensitivity.

there is more cortex devoted to areas with smaller receptive fields.

51
Q

what did Recanzone in 1992, neuroscience discover?

A

training with the 2-point task reduced threshold

training caused an increase in cortical representation of stimulation of hand.

52
Q

plasticity following injury and Kaas and Reed, 2014?

A

partial injury on the dorsal column of the spinal cord, affecting the representation of the hand in the cortex.
monkeys preferred to use the unaffected hand for reaching
- rapid improvement in hand function within first week
-pathways initially weak, largely inaffective, activating cortex but are potentiated during the recovery process.

per neuro (5 decks)

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