Neurobiology 4

Strong emotions result in both visceral motor changes and stereotyped somatic motor responses. Give some examples of each type of motor response that would accompany fear or anger for a person & then for a cat.

Visceral motor changes in both people and cats include increased heart rate, respiration, and sweating. Somatic motor responses of people are expressed through changes in facial expression while cats show an arched back, flattened ears and hiss.

Explain how the motor pathway that produces a forced or contrived smile differs from that that produces an emotional or Duchenne smile. Include all of the areas involved and where the pathway synapses and crosses the midline.

In a forced smile the umns in the motor cortex decussate at they pyramids and synapse in the facial nucleus of the contralateral side. A duchenne smile is motivated by the anterior cingulate gyrus and limbic centers following extrapyramidal projections.

Sham rage can be produced by removal of frontal cortex, white matter, & basal nuclei but leaving hypothalamus intact. What does this say about the control of complex rage behaviors such as a cat arching its back, flattening its ears and hissing?

tells us that the cerebral cortex is not necessary for complex emotional motor behaviors but the hypothalamus is essential for coordinating stereotyped somatic and visceral changes.

Which components of the limbic system are important for emotion?

amygdala, cingulate gyrus, OPFC + MPFC, ventral basal nuclei, mediodorsal nucleus of the thalamus

Which components of the limbic system are important for memory?

hippocampus, parahippocampal gyrus, mammillary body, and the anterior nucleus of the thalamus

What symptoms occur when there is extensive bilateral damage to the inferior temporal lobes?

results in placid behavior, hyperoral activity, hypersexuality, and visual agnosia

The amygdala consists of multiple nuclei that can be grouped into 3 main categories. What are they and how do they differ in terms of connections?

The medial nuclei are the smallest group and interconnected with the olfactory system. The central nuclei and interconnected with the hypothalamus and brainstem nuclei and are critical for regulating fear responses. The basolateral nuclei are connected with the cortical regions and thalamus and are heavily involved in processing sensory information and associative learning

Damage to the Medial Geniculate Nucleus of the thalamus: indicate what the behavioral outcome would be and why

The subject would have no emotional response to a tone and no conscious perception of sound. The MGN projects to primary auditory cortex for conscious appreciation of sound and to the basolateral nuclei of the amygdala to facilitate associative learning

Extensive damage to the amygdala: indicate what the behavioral outcome would be and why

The subject would become placid, decrease emotional responses such as fear and aggression, and would be unable to undergo associative learning. The amygdala processes emotions and associations but conscious perception of sensory information would remain intact

Complete destruction of the fibers connecting the central nuclei of the amygdala to the midbrain reticular formation: indicate what the behavioral outcome would be and why

The subject would show no freezing behavior but would still exhibit visceral changes in response to a scary stimulus. The connection to the midbrain reticular formation specifically controls somatic motor programs like freezing

Complete destruction of the fibers connecting the MGN to the basolateral nuclei of the amygdala: indicate what the behavioral outcome would be and why. Do you think the rat would experience subjective feelings of fear?

The subject would have no emotional fear response (and likely lose subjective feelings as well) to the tone but would still have conscious perception of the sound. The lesion blocks auditory information from the amygdala but leaves the MGN intact so sound information can still reach the primary auditory cortex.

Complete destruction of the fibers connecting the central nuclei of the amygdala to the hypothalamus.: indicate what the behavioral outcome would be and why

The subject would show no increase in blood pressure or other visceral changes but would still freeze in response to the stimulus. he hypothalamus coordinates visceral motor effectors via the autonomic nervous system. Since the connection to the midbrain reticular formation is intact, the somatic response and conscious perception remain unaffected

The initial site of associative learning that results in a previously neutral stimulus (like a tone) becoming a source of emotional significance due to pairing with a reinforcing stimulus (like a foot shock) likely occurs in the ____________. Here neurons relaying information about the neutral stimulus and other neurons relaying information about the primary reinforcing stimulus converge onto individual neurons. Learning occurs by _______________ strengthening/weakening (pick one) synaptic linkages between the previously neutral inputs and the neuron. These associations are likely maintained in conscious awareness by changes in the _____________ and _______________ cortex.

amygdala; strengthening; orbital frontal and medial prefrontal

What is the overall function of the basal nuclei?

to facilitate or initiate appropriate behaviors and emotions while simultaneously inhibiting inappropriate ones. While the dorsal basal nuclei are focused on body movements, the ventral basal nuclei perform a similar regulatory role for cognitive and affective processing

What types of information does the Nucleus Accumbens/ventral striatum receive?

receives excitatory glutamatergic inputs from the amygdala, hippocampus, pfc, and temporal cortex. It also receives dopaminergic input from the VTA

The neurons in the ventral tegmental area release ________________ onto cells of the________________

dopamine; nucleus accumbens