Brain and Behavior Exam 1

Why study brain and behavior?

•How the brain produces both behavior and human consciousness are major unanswered scientific questions.

•The brain, the most complex organ on Earth, is found in many groups of animals.

•A growing list of behavioral disorders can be explained and treated as we increase our understanding of the brain.

•Study of the brain leads to an understanding of diversity.

•Study of the brain brings insights to other fields of knowledge and is a source of employment.

Central nervous system(CNS)

The brain and spinal cord

Peripheral nervous system (PNS)

Neurons and nerve processes outside CNS

Major structures

•Cerebrum (forebrain)

•Hemispheres

•Brainstem

•Neocortex

•Cerebellum

Embodied behavior

•Our thoughts and our movements are inseparable

Mental emptiness

Subliminal movements, "total" relaxation

Sensory deprivation effects

Wildly unpleasant, loss of focus, hallucinations

Locked-in syndrome

•Consciousness can persist in the absence of sensory stimulation

Minimally conscious state (MCS)

•Increased brainstem stimulation was the key to recovery -- DBS

Persistent vegetative state (PVS)

•Like locked in syndrome, consciousness despite being fully comatose

Animal behavior

•Varies enormously

•Indicates diverse brain functions

•Produces actions that are:

-Inherited ways of responding

-Learned; plasticity

Most behaviors consist of a mix of...

•Inherited (innate; fixed) behaviors

•Learned actions that are part of cultural transmission

What are the three theories that reasoned about the causes of behavior?

•Mentalism

•Dualism

Materialism

Mentalism

•Explanation of behavior as a function of the nonmaterial mind; mind is responsible for behavior

•Consciousness, sensation, perception, attention, imagination, emotion, motivation, memory, and volition

Ancient Greece: Aristotle

•Believed the brain cooled the blood; no role in producing behavior

•Psyche

-Synonym for mind; entity once proposed to be the source of human behavior

-Nonmaterial entity governs our behavior, and our essential consciousness survives our death

René Descartes

Mind interacts with body to produce movement, working through the pineal gland at brain's center.

Dualism

•Both a nonmaterial mind and a material body contribute to behavior.

•Nonhuman animals and machines are unable to pass Descartes' tests because they lack a mind.

•The Turing test is contemporary version of Descartes's test.

Mind-body problem

•Difficulty of explaining interaction of a nonmaterial mind and a physical brain

Materialism

•Philosophical position that behavior can be explained as a function of the nervous system without recourse to the mind

Evolution by natural selection explains how...

•New species evolve and existing species change over time.

•Differential success in the reproduction of characteristics (phenotypes) results from the interaction of organisms with their environment.

Epigenetics

•Epigenetics is the study of differences in gene expression arising from environment and experience.

•Epigenetic factors do not change genes, but they do influence how genes express the traits inherited from parents.

•Epigenetic changes can persist throughout a lifetime, and the cumulative effects can make dramatic differences in how genes work.

The evolutionary approach

•Makes brain-behavior comparisons between different species.

-Gross brain size = individual intelligence?

What are the problems withe correlating brain size and intelligence...

•Difficulty in brain size measurement

•Volume or weight; body mass and measurement

•Individual differences in brains

- Body weight, gender, age, nutrition, disease or injury, stress, neurological disorders, plasticity

What are the different measurements of intelligence?

•Species-typical behavior

•General factor intelligence (Spearman's g)

•Multiple intelligences

•Flynn effect

Acquisition of culture

•Culture is learned behaviors

-Passed on from one generation to the next through teaching and experience.

-Enabled by our large brain.

•Cultural growth and adaptation render many contemporary human behaviors distinctly different from those of Homo sapiens living 200,000 years ago.

How are modern human brain sizes and intelligence studied?

•Cultural elements, ideas, behaviors, or styles that spread from person to person (memes) can also be studied within an evolutionary framework.

•Memes exert selective pressure on further brain development (ex: toolmaking)

•Most forms of mathematics and many of our skills in using mechanical and digital devices have still more recent origins.

What are the primary functions of the brain?

•The brain's primary function is to produce behavior (movement).

1.Receiving information about the world

2.Integrating information to construct a subjective experience of reality (perception)

3.Producing commands to control the movement of muscle

Afferent information

•comes into the CNS (incoming information).

- Afferent = Arriving

Efferent information

leaves the CNS (outgoing information).

Efferent = Exiting

Dorsal

structure atop the brain or a structure within the brain are dorsal

Medial

structures toward the brain's midline

Lateral

Structures toward the sides

Anterior

front

Posterior

Back

Ventral

Structures toward the bottom of the brain or one of its parts

Rostral

front like anterior

Caudal

"tail", back side

Horizontal Plane

Rostral to Caudal

Sagittal Plane

Dorsal to ventral

Coronal plane

dorsal to ventral from medial to lateral

Cerebral Protection

A triple-layered covering, the meninges, encases the brain and spinal cord, and cerebrospinal fluid (CSF) cushions them.

Cerebral cortex

-Two nearly symmetrical left and right hemispheres

-Brain folds demarcate its functional cortical zones

What are the fours lobes?

•Frontal (executive function)

•Parietal (sensory integration)

•Temporal (auditory, taste, smell, memory)

•Occipital (visual)

Cerebral Circulation

•Brain's surface is covered with blood vessels.

•Each of the three major arteries that feed blood to the cerebral hemispheres branches extensively to supply the regions shaded in pink.

•Stroke occurs with blockage or break in cerebral artery.

CSF: Interconnected Cerebral Ventricles

•Suspends the brain, acts as a shock absorber, and provides protection from mild head blows.

•Provides stable environment for optimal brain function.

Gray matter

cell bodies, dendrites, vessels

White matter

•myelin (fat)

•Corpus callosum

Neuronal Connections (tract, nerve)

•Neurons are connected to one another by fibers known as axons.

•When axons run along together, they form a nerve or tract.

•Tract = collection of nerve fibers inside CNS

•Nerve = bundle of fibers in the PNS

Spinal cord

•Controls most body movements.

•Can act independently of the brain.

Spinal reflex

•Automatic movement

•Hard to prevent (brain cannot inhibit)

•Example: knee-jerk reflex (patellar tendon)

How does the brain stem work?

•Begins where spinal cord enters the skull.

•Receives afferent nerves coming from senses and sends efferent nerves out to control movements.

•Is responsible for most life-sustaining behavior.

Brainstem Structures

-The medial view shows the relationship of the brainstem to the cerebral hemispheres.

-The shapes and relative sizes of the brainstem's three parts are analogous to your fist, wrist, and forearm.

Hindbrain

•Is evolutionarily the oldest part of the brain.

•Controls various motor functions ranging from breathing to balance to fine movements.

•Cerebellar size in humans is related to cognitive capacity.

Midbrain

Structures in the midbrain are critical for producing orienting movements, species-specific behaviors, and pain perception.

Diencephalon

The between brain, which integrates sensory and motor information on its way to the cerebral cortex; two principal parts are the hypothalamus and thalamus

Hypothalamus

•Diencephalon structure that contains many nuclei associated with temperature regulation, eating, drinking, and sexual behavior

Thalamus

Diencephalon structure through which information from all sensory systems is organized, integrated, and projected into the appropriate region of the neocortex

Hormonal Hierarchy

1. In response to sensory stimuli and cognitive activity, the hypothalamus produces neurohormones that enter the anterior pituitary through veins and the posterior pituitary through axons

2. On instructions from these releasing hormones into the bloodstream to target endocrine glands

3. Endocrine glands release their own hormones that stimulate target organs, inc;uding the brain

Forebrain

The major internal and external forebrain structures integrate sensation, motivation, emotion, and memory to enable such advanced cognitive functions as thinking, planning, and using language.

Forebrain structures

•Neocortex (cerebral cortex)

•Basal ganglia

•Limbic system

•Neocortex ("new bark")

•Allocortex

What are the structures of the cerebral cortex?

•Contains concentric rings of allocortex.

-Three-layered cortex and four-layered cortex: Allocortex

-Six-layered cortex: Neocortex

•Is most of forebrain by volume (80%); most expanded by evolution.

•Involves folding of neocortex (sulci and gyri).

Neocortex

Six-layered cortex

Allocortex

Composed of several distinct three- and four-layer structures that include the hippocampus, part of the amygdala, the cingulate cortex, several structures that make up the olfactory system, and other related areas.

Amygdala

Anxiety and fear

Cingulate cortex

Emotion formation and processing, learning, memory, linking behavior to motivation

Olfactory system

•Olfactory bulbs and receptors, pyriform cortex in front of brain, vomeronasal organ (VNO)

Limbic system

•Disagreement about structure; obsolete

What is the concept of the limbic system

•Group of structures between the neocortex and brainstem

-Principal structures: Amygdala, hippocampus, cingulate cortex

Limbic system regulates...

•Emotional and sexual behaviors

•Memory

•Spatial navigation

Controversial history in neuroscience over the limbic system...

•Obsolete term

•Recent view: Specific circuits for specific functions can be traced through several allocortical, neocortical, and brainstem structures.

Characteristics of Neocortical Layers

Distinct characteristics:

-Different layers have different cell types.

-Density of cells varies among layers.

-Differences in appearance relate to function and region.

-Cytoarchitectonic map

-Map of neocortex based on the organization, structure, and distribution of the cells.

What do the neocortical layers influence?

•Many behaviors

-Cravings, lust, interpretation of abstract concepts, words, and images

-Creates reality

Cytoarchitectonic Map of the Neocortex

•Brodmann (1909) defined areas based on the organization and characteristics of the cells he examined.

•The regions shown in color are associated with the simplest sensory perceptions:

•Touch (red), vision (purple), and hearing (orange).

•The neocortical areas that process sensory information are far more extensive than Brodmann's basic areas.

somatic nervous system (SNS)

•Monitored and controlled by the CNS.

-Cranial nerves by the brain

-Spinal nerves by the spinal cord segments

Cranial nerves involve and include...

•Twelve nerve pairs control sensory and motor functions of the head, neck, and internal organs.

•Functions of cranial nerves.

•Afferent functions

•Efferent functions

•Both functions

Cranial Nerve: I-Olfactory

Sensory; smell

Cranial Nerve: II-Optic

Sensory; vision

Cranial Nerve: III-Oculomotor

motor; most eye movement

Cranial Nerve: IV-Trochlear

Motor; moves eye to look at nose

Cranial Nerve: V-Trigeminal

Both; face sensation, mastication

Cranial Nerve: VI-abducens

motor; abducts the eye

Cranial Nerve: VII-Facial

Both; facial expressions, taste

Cranial Nerve: VIII-Vestibulocochlea

Sensory; hearing, balance

Cranial Nerve: IX-Glossopharyngeal

Both; taste, gag reflex

Cranial Nerve: X-Vagus

Both;gag reflex, parasympathetic innervation

Cranial Nerve: XI-Accessory

Motor; shoulder shrug

Cranial Nerve: XII-Hypoglossal

Motor; swallowing, speech

Vertebrae

are categorized into five anatomical regions: cervical (C1-C8), thoracic (T1-T12), lumbar (L1-L5), sacral (S1-S5), and coccygeal.

Body segments corresponding to spinal cord segments are called dermatomes with sensory and motor nerves.

SNS is...

Bilateral (two-sided)

Nerve fibers

•Posterior (dorsal in four-legged animals) fibers are afferent: they carry information from the body's sensory receptors.

•Anterior root (ventral in animals) fibers are efferent: they carry information from the spinal cord to the muscles.

•Law of Bell and Magendie

Spinal Nerve Connections

1. Fibers entering the posterior root bring sensory info from sensory receptors

2. Fibers leaving the anterior root carry motor info to the muscles

3. Collateral branches of sensory neurons may cross to the other side and influence motor neurons there

4. White-matter fiber tracts carry info to and from the brain

Visceral Relations

•Control of the viscera (internal organs), including the heart, gut, liver, and lungs, requires complex neural systems.

•ANS and ENS are hidden partners, functioning in the background as the CNS controls perceptions and behaviors.

•ANS and ENS interact with the CNS, but each has distinctive anatomy and functions.

Automatic Nervous System: ANS

•Regulating internal functions; without conscious awareness

Sympathetic division

-Forms ipsilateral connections.

-Arouses the body for action (e.g., increases heart rate and blood pressure).

-Mediates the fight-or-flight response.

Parasympathetic division

•Is opposite of sympathetic: prepares the body to rest and digest.

•Reverses the fight-or-flight response.

What is the ENS and how does it control the gut?

•The ENS is a network of neurons embedded in the lining of the gastrointestinal tract.

-Controls bowel motility, secretion, and blood flow to permit fluid and nutrient absorption and to support waste elimination.

-Functions largely independently of the ANS.

•The brain and ENS connect extensively through the ANS, especially via the vagus nerve.

-ENS sometimes called the second brain.

What is the ENS formed from?

•The ENS is formed by a network of neurons embedded in the lining of the gastrointestinal tract.

•Congregations of neurons form ganglia that send projections to the ANS and CNS, in part through the vagus nerve (cranial nerve 10), to control gut function.

Microbiome

•ENS interacts with gut bacteria, known collectively as the microbiome.

- About 3.9 × 1013 microbiota populate the adult gut, outnumbering the host cells by a factor of 1:3.

- Microbiota influence nutrient absorption and are a source of neurochemicals that regulate an array of physiological and psychological processes.

•This relationship has inspired the development of a class of compounds known as psychobiotics (live microorganisms used to treat behavioral disorders).

-Microbiota can influence both the CNS and ENS, leading to changes in behavior.

Ten Principles of Nervous System Function: 1. Neuronal circuits are a series of neurons interconnected by synapses that subserve a function when activated.

•Neuron as excitable cell (Sherrington and Adrian)

•Monosynaptic cell

•Polysynaptic cell

Ten Principles of Nervous System Function: 6. The brain is symmetrical and asymmetrical.

•Hemispheres look like mirror images, but some dissimilar features exist.

-Cortical asymmetry is essential for integrative tasks, including language and body control.

•Language is typically situated on left side; spatial functions on the right side.