Chapter 1 What are the origins of brain and behavior?
Traumatic brain injury (TBI) = a wound to the brain that results from a blow to the head.
Concussion = damage to the brain caused by a blow to the head.
1.1 The brain in the twenty-first century
What is the brain?
The human nervous system is composed of cells. Half of these brain cells are neurons and are
specialized in that they interconnect with each other and with the muscles and organs of the body
with fibers. Other half of these brain cells are glial cells and they support the functions of neurons.
Neurons send electrical and chemical signals to communicate.
The brain and spinal cord make up the central nervous system (CNS), the part of our nervous system
encased in bone. All the processes that radiate out beyond the brain and spinal cord constitute the
peripheral nervous system (PNS).
The cerebrum (forebrain) has two halves, hemispheres. The cerebrum is responsible for most of our
conscious behaviors. It enfolds the brainstem, a set of structures responsible for most of our
unconscious behaviors. The second major brainstem structure, cerebellum, is specialized for learning
and coordinating our movements.
Embodied behavior = the movements we make and the movements we perceive in others are central
to our behavior.
Locked-in syndrome = condition in which the brain is intact, functioning and sensitive to the external
world but with its nerve fiber pathways that produce movement inactivated.
Minimally conscious state (MCS) = condition in which a person can display some rudimentary
behaviors but is otherwise not conscious.
With deep brain stimulation (DBS) = neurosurgery in which electrodes implanted in the brain
stimulate a targeted area with a low-voltage electrical current to facilitate behavior, it can be
improved.
Clinical trial = consensual experiment directed toward developing a treatment.
Persistent vegetative state (PVS) = condition in which a person is alive but unaware, unable to
communicate or to function independently at the most basic level.
All these conditions reveal that the brain can be conscious to a great extent in the absence of much
overt behavior and that the brain can communicate through the signals generated by its activity.
What is behavior?
Behavior = any form of observable action or reaction of a person or animal in response to external or
internal stimuli. Most behaviors consist of a mix of inherited and learned actions.
The mixture varies considerably from species to species:
Smaller, simpler nervous system results in behaviors that depend on heredity.
Larger, complex nervous system results in behaviors that depend on learning.
1.2 Perspectives on brain and behavior
Aristotle and mentalism
The psyche: all human intellectual functions are produced by a person’s psyche. The psyche is
responsible for life, and its departure from the body results in death and is nonmaterial = mentalism
Descartes and dualism
Dualism = position that nonmaterial mind and a material body contribute to behavior in a mechanical
way. Mind produces rational behavior and body produces actions (animals have only the body part).
, Mind-body problem = difficulty of explaining how a nonmaterial mind and a material body
interact.
Darwin and materialism
All animal species are related, their brain and behavior must be related.
Materialism = behavior can be explained as a function of the nervous system without recourse to the
mind.
Natural selection = differential success in the reproduction of phenotypes results from the interaction
of organisms with their environment.
Species = group of organisms that can interbreed.
Phenotype = individual characteristics that can be seen or measured.
Genotype = particular genetic makeup of an individual.
Epigenetics = differences in gene expression related to environment and experience.
Modern and their perspectives
Eliminative materialism = if behavior can be described adequately without recourse to the mind,
then the mental explanation should be eliminated.
1.3 Evolution of brains and of behavior
Common ancestor = forebear of two or more lineages or family groups; ancestral to both groups.
Evolution of nervous systems in animals
1. Neurons and muscles evolved together and have their origins in single-cell animals.
2. Nerve net = simple nervous system that has no center but consists of neurons that receive
sensory information and connect directly to other neurons that move muscles.
3. Bilateral symmetry = the nervous system on one side of the animal mirrors that on the other
side.
4. Segmentation = division into a number of parts that are similar.
5. Ganglia = collection of nerve cells that function somewhat like a brain.
6. Spinal cord, chordates = animals that have both a brain and a spinal cord.
7. Brain.
Chordate nervous system
Cladogram = chart that branches repeatedly, suggesting a taxonomy of organisms based on the time
sequence in which evolutionary branches arise.
1.4 Evolution of the human brain and behavior
Humans: members of the primate order
Mammals are a class of chordates characterized by a large brain relative to body size. Primate order
is distinguished by especially large brain and have great color vision. Family of great apes, whose
members’ limber shoulders allow them to brachiate.
Humans are most closely related to chimpanzees, we have a common ancestor (Australopithecus).
Humans are the only surviving hominid (= primates that walk upright) species.
The first humans: Homo habilis, homo erectus, homo floresiensis, homo neanderthalis, homo sapiens
Relating brain size and behavior
Encephalization quotient (EQ) = Jerison’s quantitative measure of brain size obtained from the ratio
of actual brain size to expected brain size for an animal of a particular body size. Everything higher
than 1 have a larger brain size compared to body weight.
,Counting brain cells provides a better estimate than using weight of the brain. The density of neurons
in different brain regions are important for estimating complex behavior.
Brains become larger by the addition of neurons and the addition of neurons adds more connections
between those neurons.
Topographic = representing the different functional areas of the CNS.
Connectome = all the pathways connecting regions of the CNS.
Why the hominid brain enlarged
Climate changes.
Primate lifestyle: eating fruit, social group sizes, use of fire.
Physiological changes in the head that made the brain size increase. Efficient brain cooling
and smaller bones in the head.
Neoteny = process in which juvenile stages of predecessors become adult features of
descendant.
Prolonged stages of development allow more neurons, resulting in a bigger brain.
Changes in hominids were mediated by perhaps only a few genes.
1.5 Modern human brain size and intelligence
Meaning of human brain size comparisons
Brain’s plasticity = its ability to change.
People vary in body size, brain size and the number of brain cells and the connections between brain
cells. Any of these factors can contribute to varying kinds of intelligence, making a simple comparison
of brain size and general intelligence unwise.
Einstein’s brain was average in brain size, but he was very intelligent.
When we compare behavior across species, we are comparing species-typical behavior = behavior
displayed by all members of a species. When we compare behavior within a species, we are
comparing how well one individual performs relative to another.
Acquisition of culture
Culture = learned behaviors that are passed on from one generation to the next through teaching
and imitation.
Meme = an idea, a behavior or a style that spreads from person to person within a culture.
Recognizing the great extent to which modern human behavior results from cultural learning and
transmission is paramount to understanding how our brains function.
Chapter 2 What is the nervous system’s functional anatomy?
2.1 Overview of brain function and structure
Agenesis of the cerebellum = absence of the cerebellum
Evolution created adaptations = evolved anatomical/functional features that solved long-standing
historical problems.
The brain is plastic: neural tissue has the capacity to change in response to the world by changing
how it is organized. Neuroplasticity = the nervous system’s potential to physically or chemically
modify itself in response to environmental change and to compensate for age-related changes and
injury. Neuroplasticity is part of phenotypic plasticity = the individual’s capacity to develop into a
range of phenotypes.
Functional organization of the nervous system
CNS – brain and spinal cord: mediates behavior
, Somatic nervous system (SNS) – spinal and cranial nerves: carry sensory information from
muscles, joints and skin to CNS and transmits outgoing motor instructions that produce
movement (ipsilateral).
Autonomic nervous system (ANS): produces rest-and-digest response through the
parasympathetic (calming) nerves and flight-or-flight response through the sympathetic
(arousing) nerves (ipsilateral).
Enteric nervous system (ENS) –control the gut (ipsilateral).
Afferent (incoming) information is sensory, going to CNS. Efferent (outgoing) information is leaving
CNS.
Brain-body orientation illustrates brain structure location from the frame of reference of the human
face.
Spatial orientation illustrates brain structure location in relation to other body parts and body
orientation.
Anatomical orientation illustrates the direction of a cut through the human brain from the
perspective of a viewer.
Structures that lie on the same side are ipsilateral, if they lie on opposite sides they are
contralateral. Structures that occur in each hemisphere are bilateral. Structures that are close to one
another are proximal, those far from another are distal.
Anterior Near or toward the front of the head
Caudal Near or toward the tail
Coronal Cut vertically from the crown of the head down; used to reference the plane of a
brain section that reveals a frontal view
Dorsal On or toward the back of a four-legged animal; in reference to human brain nuclei,
above, and to brain sections, viewed from above
Frontal Of the front; in reference to brain sections, a viewing orientation from the front
Horizonta Cut along the horizon; reveals a dorsal view
l
Inferior Below
Lateral Toward the side of the body or brain
Medial Toward the middle, specifically the body’s midline; in reference to brain sections, a
side view of the central structure.
Posterior Near or toward the animal’s tail; for the human spinal cord, at the back
Rostral Toward the front of the animal
Sagittal Cut lengthways from the front to the back of the skull to reveal medial view; two
symmetrical halves
Superior Above
Ventral On or toward the belly of four-legged animals; in reference to human brain nuclei,
below
Meninges = three layers of protective tissue – dura mater, arachnoid, and pia mater – that encase
the brain and the spinal cord.
Between the arachnoid layer and the pia mater (= subarachnoid space) flows cerebrospinal fluid
(CSF) = a colorless solution of sodium, chloride and other ions. It cushions the brain so that it can
move without pressing on the skull.
The outer forebrain consists of folded and layered tissue (= cerebral cortex), bumps are gyri and
cracks are sulci, really deep sulci are called fissures. Lateral fissure and the central sulcus form the
boundaries of the lobes. Longitudinal fissure splits the brain in the two hemispheres. Frontal lobe =
performs the brain’s executive functions; lies anterior to the central sulcus. Parietal lobe = directs
