motivation
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TRANSCRIPT
Motivation
Kun-Ruey Shieh, Ph.D.謝坤叡Inst. of Neuroscience
D807, Ext. 7138/7389
Rationale
Behavior has two aspects to reflect; one is with cognitive, and the other is non-cognitive.
The latter one is the domain of motivation- or called the drive states.
Motivational states may be broadly classified into two types: (1) brought by alterations in internal physical conditions, and (2) personal or social aspirations acquired by experience.
Driving States are simple cases of motivational states that can be modeled
as servo-control systems
Set point, error signal
Temperature regulation involves integration of autonomic, endocrine, and skeletom
otor responses
The detectors of temperature have two parts; one is peripheral and located throughout the body, and the other is central and located in the anterior hypothalamus.
The mediator of temperature also have two parts; the anterior hypothalamus mediates decreases, and the posterior hypothalamus mediates increases in body temperature.
Posterior (posterolateral) hypothalamus
Anterior (anteromedial) hypothalamus
Fever
(IL-1, IL-6, TNF)
AspirinIndomethacin
Feeding behavior is regulated by a variety of mechanisms
The reason for thinking that feeding behavior is subject to a control system is that body weight seems to be regulated by a set point.
Animals often maintain the same body weight for a long period.
However, this set point can vary with stress, palatability of food, exercise, and many other environmental and genetic factors.
Dual controlling elements in the hypothalamus contribute to the control of food intake
Tg-Agouti
Normal
Other factors in hypothalamus related to feeding
Amphetamine, CCK, calcitonin, leptin: decreased the appetite
Orexin, neuropeptide Y: induced the appetite
The effects of hypothalamic lesion in feeding are thought to be due in parts of :
1. Alteration of sensory information,
2. Alteration of set point
3. Interference with behavioral arousal.
1. The destruction of trigeminal system and DAergic fibers of the medial forebrain bundle.
2. Fig. 51-5.
3. Damaged the pathways from the SNc to the ST, and from the VTA to the limbic systems (including the prefrontal cortex, amygdala, & NA).
Thirst
Drinking is regulated by plasma osmolality & extracellular fluid volume (ECF).
Osmoreceptors are located in the anterior hypothalamus.
• Subfornical organ
• Organum vasculosum of the lamina terminalis (OVLT)
OVLTPI
NH
ME
SCO
SFO
CP
AP
Thirst
Relation to Sympathetic Response
Stimulation of lateral part of hypothalamusBP increasePupillary dilationPiloerection
Stimulation of middorsal partVasodilation in muscle & vasocontriction in skin
Hypothalamus is called the cholinergic sympathetic vasodilator system.
Stimulation of dorsomedial & posterior part Secretion of Epi & NE increased from Adrenal medulla
Relation to Sleep
Lesions of posterior hypothalamus caused prolonged sleep
Stimulation of dorsal part in conscious animals caused their sleep
• However, these experiments might block or stimulate the reticular activating system (RAS) in the brain stem as their fibers passed to the thalamus & cortex
Mutations in single genes can affect certain behaviors in flies
Drosophila
Period (per) & timeless (tim) genes --- circadian rhythm
Mice
SCN
Clock mutation23.1 h
24.9 h
28.4 h
Motivational states can be regulated by factors other than tissue needs
Ecological constraints- evolutionary selection
Anticipatory mechanisms- intrinsic circadian clock
Hedonic factors-