Transduction
What is transduction?
The process through which external energy is translated into a neural signal
Explain coding.
Coding is process by which the brain turns action potentials into an understanding of the stimulus. In other words, it is how the brain reflects the physical stimulus.
What were the goals/hypotheses as well as the results of Wager et al.?
They hypothesized that if the placebo reduced the experience of pain, then there would be less activation in the pain regions of the brain. Their other hypothesis was that the reductions in the activation of the pain regions would be due to the creation of pain relief expectations. Both of their hypotheses were supported by the study, there was less activity in the regions of the brain related to pain under the placebo condition and the lower activity is moderated through a type of top-down processing.
What does it mean when we say sensory receptors are specialized for different types of stimuli?
Sensory receptors cannot respond to all stimuli about that sensation. For example, there are vibration receptors, light touch receptors, stretch receptors etc.
What are the two functional systems of vision and how are they different?
Scotopic system- black and white vision, rods
Photopic system- color, cones
Briefly explain how pain transduction occurs.
The pain receptors either respond to temperature or to a certain chemical. Once they are activated either by that temperature or chemical, specialized voltage-gated Na+ channels in the free nerve endings open and cause a depolarization.
What does the brain code for in regards to touch and pain?
Intensity, Type, and Location
Explain the case study experiment with the patient who had tactile agnosia.
The patient was given objects to touch without looking at them and then asked to both name the object and draw it. The experiment found that the patient was not able to name the objects but could draw them fairly accurately. This experiment is an example of hierarchical processing.
Explain parallel processing.
Information from each specialized receptor travels in parallel to all the other type of information being collected by other specialized receptors up into the brain. They do not converge before they reach the brain.
Do rods or cones have better acuity and why?
Cones because they are concentrated in the fovea while rods are concentrated along the sides.
Name a sensory receptor related to touch and explain how it transduces a specific external touch stimulus into a neural signal.
What is one way the sensory system conveys the strength or intensity of a stimulus?
By changing the number of action potentials firing (more action potentials= stronger stimulus).
Explain the experiment mentioned in class that determined social exclusion can cause pain.
Eisenberger et al. were curious if people can experience the emotional affective quality of pain by manipulating social exclusion. They placed participants in a brain scanner and had them play a virtual game in which other fake participants would pass the ball to each other and then begin to exclude the true participant. They found that those that were excluded experienced more activity in the anterior cingulate cortex which correlated with social distress.
What sensory receptors are more responsive to change/contrast than to absolute value and what sensory receptors are not?
Touch receptors are more responsive to change, this is why we do not feel the clothes on our skin other than when we initially put them on and take them off. Pain receptors are not. They continue to signal when pain is present, not to change. This has an evolutionary or adaptation value.
Under what light conditions do rods and cones depolarize versus hyperpolarize?
As light increases, the neurons hyperpolarize and in the dark or as light decreases, the neurons get depolarized.
How does signal amplification work in rods?
Within the intracellular transduction process, each step of the process activates more molecules and therefore amplifies the signal as it goes along the pathway.
What types of information does the visual system code for?
Color, location, motion, contrast/brightness.
Explain the findings of the study that investigated Tylenol and social pain.
The study found that participants who were socially excluded and were then given Tylenol no longer experienced activity in the anterior cingulate cortex.
Explain the pathway of hierarchical processing in the body.
It starts with the spinal cord, then the brainstem, the thalamus, the primary sensory cortex, and then the secondary sensory cortex.
What are the 3 qualities of pain? Describe them.
Sensory discriminative- physical description (i.e. throbbing, shooting)
Motivational affective- how you feel about the pain (i.e. sickening, fearful)
Cognitive quality- thoughts about the pain (i.e. mild, excruciating)
Explain how transduction occurs in rods.
Light reaches the back of the retina and hits the rods. The rods photopigment receptor is rhodopsin which breaks up when the light hits it into retinal and opsin. This leads the opsin's enzymatic site to be revealed. The opsin molecule then activates the G protein transducin. Transducin with the help of PDE converts cyclic GMP into GMP. Cyclic GMP keeps Na+ channels open so by converting it into GMP, the Na+ channels close and cause a hyperpolarization in the neuron.
How does the visual system code for color and motion?
There are 3 different types of cones that each respond to a different wavelength of light (high, medium or low). This is what allows the visual system to code for color. The Magnocellular (M) pathway conveys information about motion.
Explain the study discussed in class that asked about a potential difference in how the affective quality of pain is processed differently than the sensory discriminative quality of pain.
Rainville et al. used hypnotic suggestion to make people believe that the experience of pain was either going to be very unpleasant or not very unpleasant. They also manipulated water temperature. Some where placed in a high heat condition while others in a not so high heat condition. Their independent variable was subjective experience. To measure this, they asked the participants how unpleasant the water was and to report its sensory-discriminative quality. They found that there was much more activation of the anterior cingulate cortex when people were hypnotized to believe it would be painful than among those who were told it would not be painful. They also found that the more unpleasant the participants' reported it to be, the greater the activation.
What are the 3 main characteristics of the visual system?
Sensitivity- weak stimuli are amplified
Integration- slow signaling due to a stimulus being integrated over time
Adaptation- adapts to a wide range of light intensities
Describe the 3 temperature receptors.
TRPV1: high temperatures, capsaicin
TRPM3: higher temperatures
CMR1: low temperatures, menthol