Flashcards
Sensation and Perception Ch 14
Cards in this deck (25)
- 1What is the somatosensory system?Includes (1) the cutaneous senses (which are responsible for perceptions such as touch and pain that are usually caused by stimulation of the skin); (2) proprioception (the ability to sense the position of the body and limbs); and (3) kinesethesis (the ability to sense the movement of the body and limbs).
- 2What are the different layers of skin? What is in the skin?Epidermis: a layer of touch dead skin cells - this is the outer layer of the skin.
The dermis is the layer of skin below the epidermis.
Within the skin are mechanoreceptors, which respond to mechanical stimulation such as pressure, stretching, and vibration. - 3What are the different types of mechanoreceptors?Slowly Adapting (SA) Receptors: respond with prolonged firing to continued pressure.
Rapidly Adapting (RA) Receptors: respond with bursts of firing just at the onset and offset of a pressure stimulus.
Merkel Receptor (SA1) and Messiner Corpuscle (RA1) are located close to the surface of the skin, near the epidermis. Because of this, these receptors have small receptive fields (eg. a cutaneous receptive field is the area of skin which, when stimulated, influences the firing of the neuron).
Ruffini Cylinder (SA2) and the Pancinian Corpuscle (RA2 or PC) are located deeper in the skin so they have larger receptive fields (the Ruffini cylinder responds continuously to stimulation, and the Pancinian corpuscle response when the stimulus is applied and removed). - 4What is the pathway from skin to the cortex?Signals from all over the body are conducted from the skin to the spinal cord.
Nerve fibres transmit them to the brain along two pathways: the medial lemniscal pathway and the spinothalamic pathway.
The lemniscal pathway has large fibres that carry signals related to sensing the positions of the limbs (proprioception) and perceiving touch. These fibres transmit signals at high speed (important for controlling movement and reacting to touch).
The spinothalamic pathway consists of smaller fibres that transmit signals related to temperature and pain.
Fibres from both pathways cross over to the other side of the body during their journey to the thalamus. Most of the fibres synapse in the ventrolateral nucleus in the thalamus. Because they crossed over, signals from the left side of the body reach the thalamus in the right hemisphere of the brain and the right body ones reach the left side of the brain.
From the thalamus, signals travel to the somatosensory receiving area (S1) in the parietal lobe of the cortex and also the secondary somatosensory cortex (S2). - 5What is the hommunculus?Latin for “little man”, is a body map that shows that adjacent areas of the skin project to adjacent areas in the brain.
- 6What is tactile acuity? Two point threshold? Grating acuity? Raised pattern identification?Tactile Acuity: the ability to detect details on the skin.
Two-Point Threshold: the minimum separation between two points on the skin that when stimulated is perceived as two points.
Measured by gently touching the skin with two points (eg. drawing compass) and having the person indicate whether he or she feels one point or two
Grating Acuity: measured by pressing a grooved stimulus onto the skin and asking the person to indicate the orientation of the grating.
Raised Pattern Identification: Acuity can also be measured by placing raised patterns or letters on the skin and determining the smallest size patterns that the person can identify. - 7What is associated with better acuity?Research shows that better acuity is associated with less spacing between Merkel receptors, however this can’t be the only factor because the index finger has better acuity than the pinky finger, but the receptors are the same distance apart. Thus, the cortex also plays a role.
The areas with better acuity also have smaller receptive fields, which means that two points that are close together on the fingers might fall on receptive fields that don’t overlap and so would cause neurons that are separated in the cortex to fire (why we feel two points).
However, two points on the arm may fall on overlapping receptive fields which would cause neurons that are not separated in the cortex to fire (only feel one point). - 8How do we perceive vibration?The mechanoreceptor that is primarily responsible for sensing vibration is the Pacinian corpuscle (they respond slow to constant pushing, but respond well to high rates of vibration).
The corpuscle consists of a series of layers with fluid between each layer and transmits rapidly applied pressure (like vibration) to the nerve fibre that it surrounds, but it does not transmit continuous pressure (which means applying continuous pressure to the corpuscle should cause no response in the fibre). - 9What is surface texture? How do we view it? What does our perception depend on?The physical texture of a surface created by peaks and valleys.
Visual inspection can be a poor way of determining surface texture because seeing texture depends on the light-dark pattern determined by the angle of illumination (thus two surfaces may look different but are actually the same, and vice versa). Thus, touch provides a more accurate assessment of surface texture than vision.
Our perception of surface texture depends on how the surface is scanned and which mechanoreceptors are activated. - 10What are spatial cues? Temporal cues?Spatial Cues: provided by relatively large surface elements (such as bumps and grooves) that can be felt both when the skin moves across it and when it is pressed onto the elements.
Temporal Cues: occurs when the skin moves across a textured surface like fine sandpaper.
Temporal cues are responsible for our perception of fine textures that cannot be detected unless the fingers are moving across the surface. - 11What is the duplex theory of texture perception?The theory that there are two types of receptors involved in texture perception (spatial and temporal cues).
Research mainly focused on spatial cues but the role of temporal cues has been research recently. Experiment showed that participants who touched a surface without moving their fingers could sense little differences between two fine textures. Participants who could move their fingers had more accuracy and thus, movement (which generates vibration as the skin scans a surface) makes it possible to sense the roughness of fine surfaces.
Another experiment also showed that adapting the corpuscle to vibrations made participants less accurate in determining texture (putting vibration on fingertip for 6 mins to numb the finger, then running it over surface). - 12What happens when you use a tool to perceive texture?Research also shows that you can perceive the texture of a surface not by touching it, but also through a tool (eg. running a pen over a rough surface vs. a smooth surface - you will perceive a difference). Thus, you are perceiving vibrations from the tool, not your finger, get you can still perceive the texture of the surface.
- 13What is active touch? Passive touch? Haptic perception?Active Touch: touch in which a person actively explores an object, usually with fingers and hands.
Passive Touch: occurs when touch stimuli are applied to the skin.
Haptic Perception: perception in which three-dimensional objects are explored with the fingers and hand. - 14What distinct systems are you sing when identifying objects?(1) the sensory system, which is involved in detecting cutaneous sensations such as touch, temperature, and texture and the movements and positions of your fingers and hands; (2) the motor system, which is involved in moving your fingers and hands; and (3) the cognitive system, which is involved in thinking about the information provided by the sensory and motor systems.
- 15What are EPs? What do we relate touch to?Exploratory Procedures (EPs): a number of distinctive movements used when trying to identify an object through touch (eg. pressure - poking object, contour following - running fingers along the outside of the object, etc.)
We tend to relate passive touch to the sensation experiences in the skin (eg. I feel a pricking sensation), while we relate active touch to the object being touched (eg. I feel a pointed object) - 16What are the different types of pain?Inflammatory Pain: caused by damage to tissue or inflammation of joints or by tumour cells.
Neuropathic Pain: caused by lesions or other damage to the nervous system (eg. carpal tunnel syndrome).
Nociceptive Pain: pain caused by activation of receptors in the skin called nociceptors, which are specialized to respond to tissue damage or potential damage (a bunch of different kinds of nociceptors respond to different stimuli - heat, chemical, severe pressure, and cold). - 17What is the direct pathway model of pain?According to this model, pain occurs when nociceptor receptors in the skin are stimulated and send their signals directly from the skin to the brain.
Not completely accurate (eg. phantom limb) - 18What is the gate control model?Begins with the idea that pain signals enter the spinal cord from the body and are then transmitted from the spinal cord to the brain. It also proposes that there are additional pathways that influence the signals sent from the spinal cord to the brain.
Input to the gate control system occurs along three pathways:
Nociceptors - fibres from the nociceptors send excitatory signals to the transmission cells. Excitatory signals from the (+) neurons in the dorsal horn ‘open the gate’ and increase the firing of transmission cells. Increased activity in the transmission cells can cause more pain.
Mechanoreceptors - fibres from mechanoreceptors carry information about non painful tactile stimulation (eg. rubbing the skin). Inhibitory signals sent to the transmission cells ‘close the gate’ and decrease the firing of the transmission cells. Decrease in firing decreases the intensity of pain.
Central control - these fibres contain information related to cognitive functions such as expectation, attention, and activity also closes the gate and decreases pain. - 19What factors is pain influenced by?Expectation: Patients who were told what to expect and were instructed to relax required fewer painkillers following surgery and were sent home earlier. Patients with pathological pain get relief from taking a placebo. Another experiment gave surgery patients their pain medicine, but only told half of the patients they were receiving it. Even though it was the same medicine, those who knew they received it felt better.
Shifting Attention: the perception of pain can increase if perception is focused on the pain or decrease if the pain is ignored or attention is diverted away from it. Often you feel pain not when you are injured, but when you realize you are injured.
Content of Emotional Distraction: Experiment had participants look at either positive, neutral, or negative images while their hand was placed in cold water and were asked to keep their hand in it as long as possible. Subjects looking at positive pictures kept their hands in longer. However, when subjects rated the intensity of their pain afterwards, it was the same.
Hypnotic Suggestion: pain without activation. - 20What is the pain matrix? Multimodal nature of pain? Sensory/affective component of pain?Pain Matrix: all the brain regions that are involved in pain perception (hypothalamus, amygdala, thalamus, somatosensory cortex (S1) and S2, anterior cingulate cortex (ACC), prefrontal cortex (PFC), and the insula)
Multimodal Nature of Pain: pain is both a sensory and emotional experience
Sensory Component of Pain: eg. throbbing, prickly, or hot
Affective (or Emotional) Component of Pain: eg. torturing, annoying, frightful, or sickening
Research shows that the ACC is important for determining the affective component of unpleasantness and that unpleasantness can change even when the intensity of pain remains the same. - 21What are opioids?Chemicals in the brain that affect pain perception.
Opiate drugs act on receptors in the brain that respond to stimulation by molecules with specific structures. The importance of the molecule’s structure for exciting these ‘opiate receptors’ explains why injecting a drug called naloxone into a person who has overdosed on heroin can almost immediately revive them (because its structure is similar to heroin so it blocks the action of heroin by attaching itself to receptor sites occupied by heroin). - 22What are endorphins? What is their relationship with the placebo effect?Naturally occurring transmitters in the brain that act on opiate sites (which may be why these sites have existed in the brain long before people started taking heroin).
Endorphins can also decrease pain perception (or increase it, if the production of endorphins is blocked). Naloxone decreases the analgesic effect of endorphins and the effect of placeboes which shows that the placebo effect occurs because placeboes cause the release of endorphins.
injected subjects with chemical that causes burning sensation in each hand and each foot. Asked to rate pain at each part of the body every 15 minutes - control group rated pain at each part every time. Second group had lotion (which they were told would relieve pain) rubbed on at one or two points (placebo) - rated the pain where the lotion was rubbed as lower than other points. To show relationship to endorphins, naloxone was injected which abolished the effect.
Thus, the mind can not only reduce pain by releasing chemicals, but it can also direct these chemicals right to the locations where pain would be occurring. - 23What happens when we watch someone else being touched or experiencing pain?Watching someone else being touched or experiencing pain activates areas in the somatosensory cortex of the observer that would also be activated in the cortex of the person actually experiencing it.
Experiment showed that actually touching someone’s leg activated somatosensory areas S1 and S2, while just watching someone touch someone’s leg activated S2.
This effect did not occur when watching a plane landing - shows that it isn’t the movement that is important, but the actual perception of touch - 24What is synesthesia?A condition in which stimulation of one modality (like vision) results in an experience in another modality (like touch). When this person observes another person being touched, he or she experiences touch on the same part of his or her own body.
The effect doesn’t happen to everyone: it reflects our empathy for other people’s negative experiences. - 25What did the experiment on pain in social situations show?Experiment by Eisenberger et al.
Participants watched a computer game.
Then, they were asked to play with two other “players” who did not exist but were part of the program.
The “players” excluded the participant.
fMRI data showed increased activity in the anterior cingulate cortex and participants reported feeling ignored and distressed.
Experiment by Singer et al.
Romantically involved couples participated. The woman’s brain activity was measured by fMRI.
The woman either received shocks or she watched while her partner received shocks.
Similar brain areas were activated in both conditions.
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- 3 Psychology Flashcards on Sensation and Perception Ch 14, created by melissa_bos_66 on 27/03/2016.
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