Motivation
Motivation
• Motivation is composed of two parts,
Biological needs and Emotion.
• Both involve the hypothalamus and the
autonomic NS.
• Emotional behavior also involves the cognitive
structure of the brain along with the
autonomic NS.
Motivational States (Biological Needs)
• Are controlled by basic homeostatic regulatory
processes essential for survival; eating
drinking and sex behavior.
• Motivation varies as a function of deprivation.
• Motivational states are produced by changes
in internal conditions of the animal relative to
a given set point of the regulatory process.
• Several of the most basic issues that surround
internal motivational states are related to
survival.
• Activities that enhance immediate survival
(eating , drinking and sexing) are pleasurable
and there is a great urge to repeat these
behaviors.
• These states guide and shape our behavior for
future action.
• Internal needs require organization of
individual behavioral components into a
specific goal-oriented sequence.
• Goal attainment increases the behavioral
threshold leading to the drop off of the
behavioral components necessary for goal
attainment, leading to other classes of
behavior (i.e. the animal stops eating).
Three functions of motivational states
• 1) The have a direct function: they steer
behavior toward a specific goal.
• 2) Motivational states have an activating
function: they increase general alertness and
energize the individual to action.
• 3) Motivational states have an organizing
function: combining individual behavioral
components into a coherent, goal-oriented
behavioral sequence.
Motivation is an inferred internal state
• One can only infer from what the organism
does (behavior) as to the motivational state.
Like learning it can not be seen.
The brain circuit involved
• The hypothalamus
• There are 19 different centers in the
hypothalamus.
Hypothalamus Pituitary Interaction
• Brown study of Pineal - hypothalamus –
Pituitary interaction
• End result, molecules move from the pineal
gland to the pituitary by axonal transport and
are released into the pituitary portal system .
• The molecules circulate through the
circulatory system to reach their target organs.
Autonomic vs. Neural secretory systems
Skeltal vs. Autonomic systems
Parasympathetic vs. Sympathetic
• Parasympathetic – cholinergic – cranial sacral.
• Sympathetic – adrenergic - Thorasico-lumbar .
-
For the purpose of this class we will look at
temperature regulation as the model system
• The concept of a feedback system
• The two system inhibit one another.
Antagonistic systems
• The parasympathetic and sympathetic system
oppose one another.
Positive feedback
• For each increment of output, a part of that
out put if fed back as input. The next
increment of output is larger than the
previous output. Leads to an ungoverned out
but to self destruction.
Negative feedback
• For each increment of output, a part of that
output if fed back as input. The next
increment of output is smaller than the
previous output. Drives the system to a very
low state or zero.
Homeostasis
• First used by Claude Bernard as “milieu
interne” or internal medium.
• Developed by Walter Cannon as
“homeostasis” the attempts of the autonomic
NS to bring the biological system back to the
set point by use of the hypothalamus and the
two divisions of the autonomic NS.
• One can use the concept of set point in many
different context.: Glucostat,
The concept of set point for household use
• How does your household furnace act.
• Set a temperature (the set point) by a movable
gage. Behind the gage is a tube of mercury.
Rotating the front dial tilts the tube of mercury.
The electrode at the bottom of the tube is then
disconnected from the electrode at the top of
the tube. The furnace turns on. Heat from the
furnace expands the mercury. When contact is
made between the two electrodes, the furnace
shuts off.
The two regulatory system of the hypothalamus
controlling temperature regulation
What behaviors are exhibited when one is
cold?
• Biological (under the control of the posterior
hypothalamus):
•
Shiver; increase the rate at which glucose is
metabolized, a byproduct is heat. When glucose
stores are empty, metabolize free fatty acid.
•
Piloerrection, trap air by changing position of
hair on arms, legs and chest.
•
Remove blood from periphery to core of the
body to retain heat.
When cold
• Stimulating the posterior center gives rise to
the shivering, piloerection, chnging blood
compartments
• Behavioral:
•
Turn up the furnace.
•
Put on more close.
•
Move to a warmer room
What happens when on is hot?
• Sweat: put water on the skin.
• Change blood pool from core to periphery.
• The above two work together. Blood moved
to the skin of the periphery is a source of
energy. It take 423 small calories to break the
hydrogen bond that keeps water together on
ones skin. That much energy is given up to
remove one molecule of water from the skin
(evaporative sweating).
Eating Behavior
• Two active regions:
•
Ventromedial hypothalamus
•
Lateral hypothalamus
Ventromedial hypthalamus
• Lesion: leads to overeating (hyperphagia),
sever obesity
• Stimulation: suppresses eating (aphagia)
Lateral hypothalamus
• Lesion: sever abstention of eating (aphagia)
• Stimulation: active eating
Lesion of the lateral hypothalamus
Emotions are a sub category of motivation
• Includes the hypothalamus, Autonomic NS
and
• Portion of the thalamus, cingulate gyrus,
amygdala, hippocampus and prefrontal cortex.
Papez Circuit
Papez named this circuit the Limbic system
A (above)
• A. (two slides above) Medial view of the brain
shows the limbic lobe, which consists of
primitive cortical tissue (lighter blue area )
that encircles the upper brain stem, The
underlying structures (hippocampus and
amygdala are not visible,
B (above)
• B. (two slides above) Interconnections of the
deep-lying structures included in the limbic
system. The prominent direction of neural
activity in each trace is indicated by an arrow,
but activity in the tracts is typically
bidirectional
A system diagram of the limbic (dark
arrow) and associated corteceis
• A proposed neural circuit for emotion. The
circuit originally proposed by Papez is
indicated by the thick lines; more recently
described connections appear as thin lines.