overview: organization of the brain and behavior

Overview:

Organizationof the Brain

and Behavior

Segmental Model

Swanson, L.W. (2000) What is the brain?Trends Neurosci., 23, 519-527.

(Swanson, 2000)



Developmental Model


Evolutionary Model


Genomic Model

SYSTEM NERVORUM CENTRALE (Central nervous system)

I. ENCEPHALON (brain)

A. PROSENCEPHALON (forebrain)

1. TELENCEPHALON (endbrain; limbic system, basal ganglia & cerebral cortex)

2. DIENCEPHALON (between-brain, or interbrain; hypothalamus & thalamus)

B. MESENCEPHALON (midbrain; tectum & tegmentum)

C. RHOMBENCEPHALON (hindbrain)

1. METENCEPHALON (pons & cerebellum)

2. MYELENCEPHALON (medulla oblongata) II. MEDULLA SPINALIS (spinal cord) Notes: "BRAINSTEM" is an imprecisely defined term which usually refers to the rhombencephalon and mesencephalon together. It may or may not include the cerebellum, and sometimes the diencephalon is included.

Similarly, the terms "CEREBRUM" or "CEREBRAL HEMISHPHERES" may refer to the telencephalon or to the entire prosencephalon.

The term “BASAL GANGLIA” is also used imprecisely, sometimes including the midbrain nucleus, substantia nigra, and sometimes including only forebrain structures. The amygdala may be included as part of the limbic system or as part of the basal ganglia, depending on the author.

SYSTEM NERVORUM CENTRALE (Central nervous system)

I. ENCEPHALON (brain)

A. PROSENCEPHALON (forebrain)

1. TELENCEPHALON (endbrain; limbic system, basal ganglia & cerebral cortex)

2. DIENCEPHALON (between-brain, or interbrain; hypothalamus &

thalamus)

B. MESENCEPHALON (midbrain; tectum & tegmentum)

C. RHOMBENCEPHALON (hindbrain)

1. METENCEPHALON (pons & cerebellum)

2. MYELENCEPHALON (medulla oblongata) II. MEDULLA SPINALIS (spinal cord) Notes: "BRAINSTEM" is an imprecisely defined term which usually refers to the rhombencephalon and mesencephalon together. It may or may not include the cerebellum, and sometimes the diencephalon is included.

Similarly, the terms "CEREBRUM" or "CEREBRAL HEMISHPHERES" may refer to the telencephalon or to the entire prosencephalon.

The term “BASAL GANGLIA” is also used imprecisely, sometimes including the midbrain nucleus, the substantia nigra, and sometimes including only forebrain structures. The amygdala may be included as part of the limbic system or as part of the basal ganglia, depending on the author.

Hierarchical Organizationof the Brain

and Behavior

What is a hierarchy?

Ordering along a dimensionor

arrangement in a graded series

What are some examples of hierarchies?

Molecular biology

DNA

Cellular Proteins

Cytology

Cells

Histology

Cells and Tissues

Anatomy and Physiology

Organs

Taxonomy

Organisms

Behavior

Organisms and Societies

Complexity Hierarchy

Size Hierarchy

Command Hierarchy Partition

Command Hierarchy Lattice

Hierarchical Control by the CNS

Hierarchical sensory processing

Hierarchical motor control

Hierarchical Control by the CNSspinal cord--

basic sensory reception, integration, motor command e.g. withdrawal reflex

reflex arcs, central pattern generators

brainstem--cranial reflexes, central pattern generators (respiration,

mastication, etc)command systemsprimitive responses (orienting, posture, eye movements, etc)background pattern for more differentiated responses

(“arousal”)primitive defensive reactionsautonomic responses

subcortical forebrain--thalamus -- crude discriminations, e.g. light-dark, pain

directs retic. arousal to specific modalities (attention)limbic system -- gives rise to specific emotional stateshypothalamus -- responsive to internal chemistry

(homeostasis, hormonal regulation)

cortex--finest sensory discrimination, motor coordinationhighest integrative activity

cognition, curiosity, consciousness

Amphioxus

Encephalization

From Wikipedia (it MUST be true!):

Encephalization is defined as the amount of brain mass exceeding that related to an animal's total body mass. Quantifying an animal's encephalization has been argued to be directly related to that animal's level of intelligence. Aristotle wrote in 335 B.C. "Of all the animals, man has the brain largest in proportion to his size."[1] Also, in 1871, Charles Darwin wrote in his book The Descent of Man: "No one, I presume, doubts that the large proportion which the size of man's brain bears to his body, compared to the same proportion in the gorilla or orang, is closely connected with his mental powers."[2]

“Ontogeny recapitulates phylogeny” means thatthe evolutionary history of an organism (its phylogeny) is recapitulated (repeated) in its ontogenetic (lifespan) development.

In ontogeny, “encephalization” means a relative increase in the importance of progressively more rostral structures of the brain.

We will critically examine these notions as the course progresses.

Organization of Behavior

Behavior Also Can be Organized

HierarchicallyReflexes

Rhythmic Behaviors

Kineses

Taxes

Species-typical (“instinctive”) behaviors

Motivated (operant) behaviors

Latent learning



predictable, stereotyped responsesto specific stimuli•usually localized•involuntary•involve relatively few neurons•graded responses•degree of voluntary control over reflex varies



Micturition reflex is well-controlled•"to pee or not to pee"•elicited by distention of bladder•bladder contraction and internal sphincter relaxation

spinal control•external sphincter relaxation

brainstem control•external sphincter relaxation under cortical inhibitory control•eventually, however, control must give way

Pupillary reflexes are generally not subject to significant voluntary control



Rhythmic Behaviors

basis of rhythmic behaviors are Central Pattern Generators (CPGs)

•in brainstem and spinal cord•mechanisms that can operate without any sensory input•run a sequence of movements, like computer programs•input may be necessary to initiate them

• underlie activities as diverse as chewing, breathing, locomotion, and copulation, even music and speech

•long thought to be reflex activities•reflexes act as modifiers via feedback control



Rhythmic Behaviors

Kineses•change in rate of movement•simple change in rate of rhythm (CPG)•may be + (increase in rate) or

– (decrease in rate)•named according to evoking stimulus

• e.g. + photokinesis, – thermokinesis•general to the species•serve to maximize time in good environment, •minimize time in bad environment•often incorrectly inferred to reflect higher-order processes•e.g. formation of aggregates



Rhythmic Behaviors

Kineses

Taxes•movement oriented to a stimulus•may be + (approach) or – (withdraw)•named according to mechanism, type of stimulus•klinotaxis

• single receptor integrating over time•tropotaxis

• paired receptors--simultaneous comparisons•telotaxis

• orientation toward a goal• not necessarily stimulus strength

• e.g. swim to shore



Rhythmic Behaviors

Kineses

Taxes

Species-typical (“instinctive”) behaviors•a.k.a. fixed action patterns•relatively complex behaviors common to members of a species•require minimal learning at most•usually referred to as innate or instinctive



Rhythmic Behaviors

Kineses

Taxes


Motivated (operant) behaviors•goal directed•elicited by physiologically meaningful stimulus•signals food, sex, water, threat, etc.•terminated by consummatory response• eat, drink, fight, flee, copulate•appetitive—approach, aversive-- withdraw



Rhythmic Behaviors

Kineses

Taxes

Species-typical (instinctive) behaviors


Latent learning (learning without a US)•by observation (modeling, imitation)•by performing without reward•by exposure



Rhythmic Behaviors

Kineses

Taxes



Latent learning

overview: organization of the brain and behavior

Documents

term basal ganglia

trends neurosci

basal ganglia cerebral

cerebral hemishpheres

entire prosencephalon

defined term

midbrain nucleus

prosencephalon forebrain1