Perception

Figure 7.17 Receptive fields and adaptation rates of touch receptorsKlein/Thorne: Biological Psychology© 2007 by Worth Publishers

Somatosenses

• Pacinian corpuscles– Hairy and hairless skin– Joints, muscles, internal organs, etc– Sense high frequency vibrations– Largest sensory receptors in body– Large receptive fields

Somatosenses

• Free nerve endings– Hairy and hairless skin– Sense temperature change (firing rate

corresponds to heat or cold)– High threshold and low threshold– Sense pain

• Fast pain: injection, cut; mylineated type A fibers• Slow pain: cell damage; unmylinated type C fibers

How does sensory information get from skin to the brain?

From skin to brain

• Neurons carry sensory information from cutaneous receptors

From skin to brain

• They reach the spinal cord, gather together as they enter spinal cord, and carry that info to the brain

Figure 2.10b DermatomesKlein/Thorne: Biological Psychology© 2007 by Worth Publishers

Mapping the Somatosensory Cortex

• Take people who are wide awake, under local anesthesia

• Stimulate different parts of sensory cortex sensations in various parts of the body

Figure 7.19 The somatosensory cortexKlein/Thorne: Biological Psychology© 2007 by Worth Publishers

Pain

The Gate Control Theory of Pain

What’s the “gate” in “gate control theory”?

• Periaqueductal gray (PAG) in midbrain

• Inhibitory interneurons in spinal cord and lower brain stem

• Figure 7.20

What’s the “gate” in “gate control theory”?

• Nerve fibers carry pain messages to the spinal cord

• There are “gates” in the spinal cord that control how much of the pain messages actually get to pass through to the brain

• The brain sends signals to the spinal cord to control how much the “gate” is open or shut

• Activity in PAG activates inhibitory interneurons blocks pain from entering brain

What causes the “gate” to be open?• Physical reasons

• Cognitive (mental) reasons

• Emotional reasons

Soldiers vs. civilians

WW-II Soldiers• Severe combat

wounds• One out of 5 needed

morphine

Civilians• Trauma wounds

• One out of 3 needed morphine

X

Soldiers vs. civilians

WW-II Soldiers• Severe combat

wounds• One out of 5 needed

morphine• Meaning of injury:

survived the battlefield, were returning home

Civilians• Trauma wounds

• One out of 3 needed morphine

• Meaning of injury: prospect of surgery, loss of job/income, disability

X

• Anterior cingulate cortex– Emotional aspects of pain

Phantom Limb Pain

Neuromatrix Theory of Pain

• Explains things about pain that gate control theory does not explain

• Neuromatrix: map of body parts in neocortex– Phantom limb pain

The Motor System

Movement

http://news.bbc.co.uk/2/hi/science/nature/7423184.stm

Figure 8.13 The cortical control of movementKlein/Thorne: Biological Psychology© 2007 by Worth Publishers

Figure 8.14 Rhea hitting a fairway ironKlein/Thorne: Biological Psychology© 2007 by Worth Publishers

1. Dorsolateral Prefrontal Cortex• Plan and prepare for movement

• Takes information from senses to decide next movement

2. Secondary Motor Cortex• Supplementary motor area and premotor cortex

• Planning and sequencing movement, based on info from dorsolateral prefrontal cortex

• Study regarding monkey and pushing a peanut through a hole

3. Primary Motor Cortex

Figure 8.13 The cortical control of movementKlein/Thorne: Biological Psychology© 2007 by Worth Publishers

4. Primary Somatosensory Cortex

• For example, senses from muscles and joints

5. Posterior Parietal Cortex

• Combines info from what you see, hear and feel on your skin– E.g., golf, locating light switch in the dark

Other parts of the brain involved in movement

Cerebellum and Basal Ganglia

Cerebellum

The Cerebellum

• Movements that require accurate aim

X

The Cerebellum

• Movement of eyes to focus on something

• Speech

X

The Basal Ganglia

• Controls posture and muscle tone

Figure 2.23 The basal ganglia Klein/Thorne: Biological Psychology© 2007 by Worth Publishers

Parkinson’s Disease

• Not enough dopamine being produced in substantia nigra, less dopamine to basal ganglia

• Movements are rigid and slow

• Tremors

• Problems with starting to move and think

• Contralateral– Different side

• Ipsilateral– Same side