Course Outline | Intro to Psych | EnvironmentalET

Biological Psychology

The Mind?


Rene Descartes, the seventeenth century father of modern philosophy, said "Cogito ergo sum." For Descartes, his mind was an indisputable fact. His body, and the outside world, could be illusion.

Descartes divided the universe into mind and everything else, a philosophy known as Cartesian dualism.

Most of us hold to this on a common sense level. We subjectively view our consciousness to be distinct from the objects of our observation (even when we are observing our own bodies).

Descartes proposed that the body was a machine but that the soul was intangible. The two were connected via the pineal gland.

His view can be called interactionism

About 100 years after Descartes, a French physician named Julien de La Mettrie noticed how dramatically a fever affected his own mental state. He wrote a book entitled The Natural History of the Soul (L'histoire naturelle de l'âme) in which he asserted that the soul and no different than the mind and that both were part of the body, which was essentially a machine.

La Mettrie had been a priest before he went into medicine, but as you can imagine, this book got him into trouble with the Church.

His philosophy can be called monism or materialism, the belief that the world is composed of one sort of stuff (matter).

In 1861, a French doctor named Paul Broca studied a man who could not speak coherently following a head injury.

A post-mortem revealed damage to an area of the left frontal lobe now called Broca's area.

This is considered to be the first empirical evidence connecting behavior to specific brain regions.

There is now considerable evidence of localization of function, that is brain structure and activity that corresponds in reproducible and specific ways to behavior or states of mind.

Current biological psychology does not support Descartes: Based on experimental evidence, it appears that the soul (if it exists) is completely dependent on brain activity.

Until the 1960's, even the concept of "mind" was not entirely accepted, though today cognitive psychology finds it to be useful.

Scientists generally do not hypothesize the existence of the soul for two reasons:

  1. It is not directly observable and therefore is not subject to experimental tests.
  2. It is an unnecessary complication. Existing data can be explained without it (ever hear of Occam's razor?).

Still, there is certainly no "proof" that the soul does not exist. Similarly, there are a number of reasonable philosophical arguments against reductionism.

In general, biological psychologists are reductionist. They believe that behavior (and experience) can be reduced to biology and explained in its terms.

The success of chemical treatments for depression and anxiety may support this view.

The Death (and Rebirth) of the Homunculus

In cartoons or our imagination (even in Woody Allen movies) we see the brain and mind as a vast complex, like a machine, a factory, or a city.

In charge of this city is a little person (a "homunculus" in Latin) who sits somewhere behind our eyes.

This little person receives all our sensory input, looks up things in our memory banks, makes a decision and issues a command.

Suppose that I am at a buffet, deciding whether to have pizza with double cheese (dripping with grease) or salad with fat-free vinaigrette.

In the homunculus model, my inner person takes note of the smell from the pizza, sees the rising steam, etc. That is combined with memories of previous delicious indulgences. On the other hand, he recalls stories of heart disease and perhaps memories of heartburn. Maybe he takes a reading on some sort of guilt meter. He weighs the alternatives and then announces in my mind "I think I'll have the pizza." Shortly thereafter, he sends a signal to the hand to go for the cholesterol pie.

This idea is similar to the idea of the "ghost in the machine," an immaterial entity that inhabits our body and makes our decisions. According to Descartes and to many other thinkers, this ghost is who we actually are.

Obviously there is no little man, but we might hypothesize that there is some sort of "central processing unit" or "executive circuits" in the brain.

Cognitive scientists believe that the mind (and the brain) have a modular organization. One or more of the modules may have "executive" functions. Think about the role of attention in perception (we will discuss in a couple of weeks).

Normal functioning of the mind involves many processes dependent on many structures in the mind. The frontal lobes seem to be especially important in planning and decision making.

Still, brain scans would show that the motor impulses driving my hand toward baked heart attack initiate in certain parts of my brain before I was even aware of my decision to have pizza.

Behaviorists such as BF Skinner used the problem of infinite regress to dismiss the idea of a central consciousness in the mind. If consciousness is a little man in the head, what is conscious in the little man's head?

There is one sense in which there is a little person in the brain. The motor cortex stretches left and right from the center line (the longitudinal fissure) of the brain along the ridge at the back of the frontal lobe. (This ridge runs in front of the central fissure, so it is called the precentral gyrus). In this ridge are the cell bodies of neurons that initiate voluntary movements. Each point on this ridge corresponds to a muscle somewhere in the body. Adjacent areas of the motor cortex control adjacent areas of the body, though the relative size of the cortical areas is distorted relative to the size of the body part (see figure 4.10 on page 67 in Myers). This mapping of body to brain is called the "motor homunculus."

Likewise, in back of the central fissure, at the front of the parietal lobe is a ridge (the postcentral gyrus) with the cell bodies of sensory neurons receiving info from different areas of the body. This is called the "sensory homunculus."

This sort of topographic organization is found in many areas of the brain, for example in the visual cortex.


There is a thorough set of online tutorials on neurons and the brain, with pictures, from Athabasca University at

The Neuron

The nervous system depends on specialized cells called neurons. The brain contains about 100 billion neurons.


Like all cells, neurons are surrounded by a cell membrane.

The membrane consists of a lipid bilayer.

Neurons are mostly fat by dry weight.

A number of biochemical structures are imbedded in the lipids, including:

ion channels - allow ions (like sodium or chloride) to pass through the membrane

receptors - respond to the chemical environment outside the cell

Neurons have three parts:

cell body

nucleus - contains the genetic material of the cell

metabolic functions

The gray matter of the brain and spinal cord has a high density of cell bodies.

one axon

carries signals away from the cell body

branched at the end, each branch tipped with a terminal button

presynaptic membrane releases messages to other cells

The white matter of the brain and spinal cord is composed largely of myelinated axons (nerve fibers).

Note: A "nerve" is a bundle of axons. There are axons in the body several feet long (for example, from your spine to your toes).

one or more dendrites

carry signals toward the cell body

post synaptic membrane receives messages from other cells

There is a high density of dendrites in gray matter as well; there is much communication between neurons here.


Action Potentials

Every living cell maintains chemical differences between the extracellular environment and the cytoplasm inside the cell.

Sodium ions are actively pumped out of the cell, creating a negative charge inside the cell (about 70 mV in neurons at rest).

When properly stimulated, neurons open ion channels in the cell membrane, allowing sodium ions to enter the cell, reducing then reversing the membrane potential to about +40 mV.

When one point on the membrane is discharged, it can induce discharge in an adjacent point. Thus the discharge is conducted along the membrane (down the dendrite or axon).

About a millisecond after depolarization, the membrane begins pumping ions again until the resting potential is restored.

The impulse travels along the neuron as a transient point of depolarization.

Most neurons in the brain and many elsewhere are myelinated, ie covered with an insulated sheet (actually formed by another cell called a Schwann cell). The myelin sheath has regular gaps in it and the discharge jumps from gap to gap, travelling more quickly and reliably than down an unmyelinated membrane.

In multiple sclerosis, the myelin sheath breaks down.

The entire sequence is called an action potential or nerve impulse.

Synaptic Transmission

Nerve cells communicate with each other.

The cells do not touch each other but rather are separated by a very thin gap called a synapse.

The action potential cannot cross this gap, the signal is instead carried by chemical messengers called neurotransmitters (NT).

The action potential reaches the terminal button.

Within the terminal button synaptic vesicles (tiny sacs of neurotransmitters) moved toward and merge with the presynaptic membrane.

The synaptic vesicles release their contents into the synaptic cleft.

The neurotransmitters cross the synapse and reach receptors on the postsynaptic membrane.

Receptors are specialized biochemical structures (mostly protein) that match a particular neurotransmitter.

The NT is the "key" that fits the receptors "lock."

Receptors are on dendrites, or sometimes cell bodies, of other neurons.

The receptor responds in one of two ways:

Excitatory transmitters increase the likelihood of an action potential in the postsynaptic cell.

Inhibitory transmitters decrease the likelihood of an action potential.

Either can carry a message--in the absence of synaptic events, a neuron fires at a baseline rate. The signal can be in the form of an increase or decrease in firing rate.

Following release and receptor activation, the NT is deactivated by degradation (being broken down by enzymes) or reuptake (being put back into vesicles inside the neuron).

Putting it together

The function of the nervous system depends on the combined activity of many neurons.

Each neuron receives synaptic transmissions from many other neurons. The cell combines the multiple excitatory and inhibitory messages and either fires or not.

A cell membrane can be partially depolarized, but an action potential is all-or-none.

Structure of the Nervous System(s)

Organization of the Nervous System(s)

The central nervous system consists of the brain and spinal cord.

Neurons in the CNS divide and grow up to about age 6 and then stop.

Damage to the CNS (such a spinal injury) is not usually repaired by regeneration of the damaged tissue.

Brain damage is often overcome because other cells will take over functions previously carried out by the damaged tissue.

There are also non-neuronal cells in the CNS that serve structural roles. These continue to divide (and in fact can become cancerous).

The peripheral nervous system consists of the nerves that run to the body from the spinal cord, as well as the cranial and facial nerves (that run directly out of the brain).

PNS nerves continue to grow and divide throughout your life.

Damage to the PNS is usually repaired.

The Brain

The Three Brains

Paul McClean was working on a theory of the "triune brain" as early as the 1950's

There are a number of schemes for dividing the brain into three parts, the details do not always agree.

The basic idea is that the higher most human functions (such as reason and language) are dependent on the newest, outermost and topmost layer (the cerebral cortex).

More primitive functions such as emotions, are localized in brain structures within or below the neocortex.

The most primitive functions are localized  in the deepest parts of the brain.


Cerebral Cortex (neocortex)

frontal lobe
temporal lobe
parietal lobe
occipital lobe
cerebellum (sometimes included in the hindbrain)
corpus callosum

voluntary motion

New Brain (forebrain)

Limbic System (subcortex)



sensory preprocessing
basic drives (4Fs)
motion sickness

Mammalian Brain

Reptilian Brain

Brainstem (and company)(old brain)

locus coeruleus
substantia nigra

reticular formation
medulla oblongata

visual and auditory processing
eye movements
normal motor function

basic bodily processes

The Brainstem

This part of the brain is shared by a wide group of organisms (virtually all vertebrates). It is the "oldest" part in evolutionary terms. Damage to the brainstem is usually fatal.

The medulla is a swelling on the top of the spinal cord. It regulates basic processes such as heart rate, breathing, blood pressure, sneezing, coughing, etc.

The pons connects the neocortex and the cerebellum.

Spread through the brainstem (and into the limbic system) is the reticular system. This controls sleep and arousal.

The midbrain contains the locus coeruleus, part of the reticular system. It is also involved in vision and hearing. It regulates visual tracking.

The Limbic System

We have the limbic system in common with some lower vertebrates. It includes the "mammalian brain" and perhaps parts of the "reptilian brain."

The limbic system is involved in the four Fs:

Family Matters J

Thalamus is a sensory relay station, receiving sensory information (except olfactory) and sending it to other parts of the brain. Sensory information (eg, visual stimuli) can influence feeling and behavior here even before or without conscious awareness (ie, cortical involvement)

Victims of cortical blindness can still respond reflexively or emotionally to visual cues.

Hypothalamus, located below the thalamus, has several vital roles in keeping the organism alive. Damage to the hypothalamus can easily be fatal, or cause severe abnormalities (gluttony or starvation).

Controls the autonomic nervous system



Amygdala appears to be crucial in anxiety, fear, violence and aggression, as well as learning and memory relative to intense emotional experience.

Hippocampus has been proposed as a resonant circuit active in short term memory. It may play a crucial role in motion sickness.

The Cortex

The cortex is evolutionarily the "newest" part of the brain; it is also called the "neocortex." Damage to the cortex is not usually fatal. It may even be unobservable.

The human cerebral cortex is larger and more complex than that of any other animal. The cortex is like a large sheet of "neuron paper" crumpled over the limbic system. (Cortex means "bark").

Many areas of the cortex can be mapped onto sensory or motor functions of parts of the body or may be related to specific memories, sensations or experiences.

This mapping and specificity is taken as evidence that the mind is at least tied to the brain.

Cortical function:

localized yet diffuse
plastic (one area can take over the functions of another, temporarily or permanently)

The cortex is divided into two grossly symmetrical hemispheres. Each hemisphere is divided by large fissures (grooves) into four lobes.

Function is divided between the hemispheres (lateralization)

Speech is in the left hemisphere for right handed males.

For lefties the functions may be reversed.

For females the functions may be more shared.

Frontal lobe is forward of the central fissure, behind your forehead.

primary motor cortex (aka frontal motor area)

located along the central fissure

involved in voluntary movements

damage causes loss of specific fine motor skills (especially of the fingers)

the degree of coordination in a body region (eg, the hands) corresponds to the size of the connected area in the motor cortex

Broca's area

only in the left hemisphere

crucial for speech

other frontal areas (association areas)

involved in emotion and integration of experience

no obvious sensory or motor function

surgical destruction of this area (called a frontal lobotomy) reduces emotional expression, and was previously attempted to control extreme manic symptoms

Parietal lobe is behind the central fissure and above the lateral fissure, below the back of the top of your head.

sensory cortex (aka primary somatic projection area)

just behind the central fissure (across from the motor cortex)

receives tactile information from the body

mapped similarly to the motor cortex

Temporal lobe is below the lateral fissure, beneath your temples.



Wernicke's area

left hemisphere

speech recognition

Occipital lobe is in the back of the head.


damage to this area can impair visual function

cortical blindness

visual agnosia

I also include the cerebellum and corpus callosum in the cortex (for lack of somewhere else to put them)

Cerebellum (Latin for "little brain")

tucked below the temporal and occipital lobes (sticking out of the bottom of the brain)

active in the control of complex movements

appears to be a set of tuned circuits that can create "movement subroutines" launched in whole by the cortex

also hemispherically divided

connected to motor cortex and sensory nervous system via the brainstem

Corpus callosum (Latin for "tough stuff")

a dense band of nerves connecting the left and right hemisphere

located underneath the cortical lobes and above the limbic system

allows communication between the hemispheres

if this is severed, a the two hemispheres seem to function independently

The Peripheral Nervous System

Autonomic Nervous System

The autonomic nervous system controls "involuntary" functions of the body such as digestion, circulation, breathing, and so forth. It connects the CNS to glands, smooth muscles (eg, in the intestine), and internal organs. It has two main circuits:

The sympathetic division is associated with arousal, agitation and utilization of energy.

The parasympathetic division is associated with calmness, relaxation, and conservation of energy.

Somatic Nervous System

The somatic nervous system conveys "conscious" sensations and "voluntary" actions. It connects the CNS to sense receptors and striated (skeletal) muscles.

Sensory (afferent) neurons carry sense impulses to the CNS.

Motor (efferent) neurons carry motor impulses from the CNS.



These chemicals are released by neurons to effect a change in another neuron or in some other structure (like a muscle cell).

There are now thought to be as many as 100 different chemicals involved in nervous transmission.

Some NTs:

acetylcholine (ACh)

the first identified NT

active in the parasympathetic nervous system

triggers muscle contractions when released by motor neurons onto muscle cells

nerve gas and pesticides work by preventing the breakdown of ACh

active in cognitive functions

Alzheimer's Disease is associated with a loss of certain cholinergic neurons in the brain

nicotine is an ACh agonist (ie, it simulates the effects of choline)

dopamine (DA), norepinephrine (NE)(aka noradrenaline), and epinephrine (E)(aka adrenaline)

chemically similar

active in the sympathetic nervous system

implicated in depression (a lack of DA)

drugs that block the breakdown (MAOIs) of DA are used to treat depression

implicated in anxiety (an overabundance of NE)


implicated in arousal by the reticular system

g-Aminobutyric Acid (GABA)

a critical inhibitory NT

slows down firing rates throughout the nervous system

alcohol, barbiturates, and BDZs (eg, Valium) act at the GABA receptor complex

alcohol and barbiturates act at different active sites in the receptor and are sometimes fatally synergistic

Glutamic Acid (Glu)

excitatory in CNS

MSG (in Chinese food) is monosodium glutamate, the same compound

some people report headache and sensory abnormalities after eating food containing MSG


The endocrine system consists of a set of glands that release chemicals, called hormones, into the bloodstream.

Hormones are chemicals (secreted by endocrine glands or even the brain itself) which affect the long term (minutes, days, years) functioning of the body.

Some hormones are chemically identical to neurotransmitters.

The function of the endocrine system is slower than the nervous system, but is complementary to it.






circadian rhythm


growth hormone

stress response (long term)
lactation and labor






calcium and phosphorus metabolism


insulin, glucagon

carbohydrate metabolism

Adrenal Medulla

epinephrine, norepinephrine

stress response (short term)

Adrenal Cortex


carbohydrate metabolism
electrolyte balance

Gonads: Ovaries/Testes

sex hormones

secondary sex characteristics
pregnancy/sperm production
sexual behavior

The pituitary gland, located on the edge of the brain, is the "master gland" that mediates between the hypothalamus and the rest of the endocrine system.

The pituitary can directly influence the nervous system; the hypothalamus can relese hormones to the bloodstream.

Neuropeptides are short amino acid sequences that function as both neurotransmitter and hormone.

Studying the Brain

Electrical Stimulation of the Brain

In the 1950s, Delgado et al and Olds & Milner discovered that electrical stimulation of the limbic system could produce pain or pleasure in experimental animals (actually, it was observed to be aversive or rewarding). The stimulated areas have been called the pain and pleasure centers of the brain.

Before his death in 1976, a neurosurgeon named Penfield pioneered the treatment of epilepsy by electrically destroying a small volume of neurons that had acted as a seizure focus.

Patients were awake during surgery (the brain itself is insensitive to pain). To orient himself in the cortex, Penfield would stimulate a small area and ask the patients to tell what they were experiencing. A range of sensory and motor responses were recorded. In some cases elaborate memories could be vividly evoked by electrical stimulation.

Split Brain Phenomena

In the 1960's Bogen and Sperry studied patients in whom Bogen had cut the corpus callosum to control severe epilepsy.

The epilepsy was reduced (for reasons that were not entirely understood).

The patients seemed largely normal, except:

Stimuli presented to one hemisphere was immeidately available only to that hemisphere.

An object was placed in the patients left hand. Because the sensory information crosses to the opposite cortex, the identity of the object is known to the left hemisphere. Speech is localized in Broca's area in the right hemisphere, and in fact the patient's could not readily say what the object was. They would recognize it if placed in the left hand again.

Similar effects could be demonstrated when visual stimuli were presented to the left visual field (the right hemisphere).

Sperry was awarded the Nobel Prize in 1981.

Brain Scans

electroencephalogram (EEG)

a measurement of electrical potentials at points around the brain, usually outside the skull

not very sensitive (generally reflects the sum of all electrical activity in a region)

also, the brain is well-insulated electrically

certain "brain waves" associated with mental states (eg, alpha waves with relaxation)

magnetoencephalogram (MEG)

the brain is not well shielded magnetically

using superconducting magnetic detectors (superconducting quantum interference devices--SQUIDs), high resolution may be possible

computerized axial tomography (CAT) scan

uses a large number of conventional xrays taken from different angles, then combined in a computer

reveals structural abnormalities

positron emission tomography (PET) scan

detects emission of positrons from radiolabeled glucose (usually 15O)

lights up areas that are actively taking up glucose, the brain's energy source

magnetic resonance imaging (MRI)

looks at water density or other chemical characteristics

reveals structural abnormalities

functional magnetic resonance imaging (fMRI)

can show biochemical activity in space and time

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Course Outline

Intro to Psych


Anthony G Benoit
(860) 885-2386