Lecture 23 The Chemical Senses Flashcards
How do you perceive texture with a pen?
- turn your pen over (or cap it) so you can use it as a probe
- hold pen at one end and move the other end over something smooth
- notice you can sense smoothness of a page
TRUE or FALSE: neurons further downstream become more specialized
FALSE: upstream
neurons in the _____________________ have center-surround receptive fields (like in the __________)
ventral posterior nucleus; LGN
TRUE or FALSE: some somatosensory neurons respond maximally to particular orientations and/or direction of movement
TRUE
___________ can also modulate the response of neurons in S1 and S2.
attention
What study results suggest that attention can modulate response of neurons in S1 and S2?
- raised letters run across monkey hands
- attention on tactile sensation vs. attention on unrelated visual stimuli
- more robust firing in TACTILE-ATTENTION condition
What is pain?
multimodal phenomenon containing a SENSORY and AFFECTIVE/EMOTIONAL component
What are the different types of pain
inflammatory, neuropathic, nociceptive
What is inflammatory pain caused by?
damage to tissues and joints or by tumour cells
What is neuropathic pain caused by?
damage to CNS (e.g. carpal tunnel syndrome, SCI, etc.)
What is nociceptive pain caused by?
activation of nociceptors in the skin, which signal impending damage
What do nociceptors respond to?
heat, chemicals, severe pressure, cold
Describe the balance required for threshold of eliciting nociceptor response?
WARN system of damage without being OVERSENSITIVE (i.e. not be triggered by normal activity)
What is the direct pathway model of pain?
pain = nociceptors being stimulated and sending signals to the brain
What is the problem with the direct pathway model of pain?
exceptions including:
- pain can be affected by mental state
- can occur when no stimulation of skin
- can be affected by attention
- phantom limb
What is the gate control model of pain?
- pain signals enter spinal cord from body and transmitted to brain
- various pathways influence transmission of these signals from SC to brain –> open/close gate that these signals flow through
- integrates 3 types of signals processed in DORSAL HORN of SC
- integrated output sent to TRANSMISSION CELLS (directly related to perception of pain)
What are the 3 types of signals processed in the dorsal horn? Which ones open/close the gate?
- MECHANORECEPTORS: non-painful tactile-based stimuli –> (-) close gate
- NOCICEPTORS: painful tactile-based stimuli –> (+) open gate
- CENTRAL CONTROL: receive signals related to cognitive function (attention, expectations, etc.) –> (-) close gate
______________ has been used to keep patients’ attention on other stimuli than the pain-inducing stimulation.
VR technology
TRUE or FALSE: when surgical patients are told what to expect, they request more pain medication and leave the hospital later
FALSE: expectation –> LESS pain meds, leave hospital EARLIER
Another example of expectations mediating pain can be seen with ______________, which can be very effective at reducing pain
placebos
How did Bingel et al. 2011 systematically vary expectations for pain?
- all conditions attach saline IV line and calibrate intensity of a painful stimulus until participants reported 70/100
- baseline: no painkiller given
- no expectation: patients NOT TOLD saline switched to painkiller
- positive expectation: patients TOLD saline switched to painkiller
- negative expectation: patients NOT TOLD saline switched to painkiller, but WARNINGS pain level may increase
What did Bingel et al. 2011 find from their study on varying expectations for pain?
robust effects of expectations, INDEPENDENT OF PRESENT OF PAINKILLER
What is a nocebo effect?
increase in pain accompanying negative expectation condition
TRUE or FALSE: participants kept their hands in cold water for longer when they were shown negative pictures
FALSE: LONGER for POSITIVE
