Biologisk psykologi & neuropsykologi - Linköping University · neuropsykologi Thomas Karlsson IBL,...

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Biologisk psykologi &

neuropsykologi

Thomas Karlsson

IBL, Linköpings Universitet

• Föreläsningar

• Seminarium—obligatoriskt

• Gruppövning—obligatoriskt

Seminarum och gruppövning kräver inga

särskilda föberedelser, utöver att ha last

litteraturen.

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Galen

• Claudius Galenus of Pergamum(131-

201 AD), better known as Galen, was an

ancient Greek physician. His views

dominated European medicine for over

a thousand years.

• Brain—not the heart—site of the soul

Two basic questions

• The fundamental organ—the brain

• The fundamental unit and it’s mode of

operation—the neuron

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The relation between brain

structure

and function (a)

The relation between brain

structure and function (b)

Source: Carlson, N.R., Physiology of Behavior (6th edition), p. 235. Boston: Allyn & Bacon, 1988. © Allyn & Bacon.

Reproduced with permission.

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Sagittal views of the human brain

(a)

Source: Reprinted from England, M.A. and Wakely, J. (1991) A Colour Atlas of the Brain and Spinal Cord, p. 76. © 1991, by

permission of the publisher Mosby.

Sagittal views of the human brain

(b)

Source: Reprinted from England, M.A. and Wakely, J. (1991) A Colour Atlas of the Brain and Spinal Cord, p. 76. © 1991, by

permission of the publisher Mosby.

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The Four Lobes and the

Sensory-Motor Processing Areas

The Four Cerebral LobesTable 2.5 The Four Cerebral Lobes and Type of Sensory/Motor

Processing in Each Lobe

Cerebral Lobe Type of Sensory/Motor Processing

Frontal Includes motor cortex, which allows us to move the

different parts of our body

Parietal Includes somatosensory cortex where our body

sensations of touch, temperature, limb position, and

pain are processed

Temporal Includes primary visual cortex where visual

sensory information is initially processed

Occipital Includes primary visual cortex where visual

sensory information is initially processed

Ou

tside

“Insid

e”

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Broca's Area and Wernicke's

Area

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Insula

Anterior cingulate

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The principal parts of a neuron

and its connections with other

neurons

An Intriguing Puzzle

• Neuroscience

– Scientific study of the brain and nervous system

• Connectome

– Totality of connections between neurons in the

nervous system

Neurons and Glial Cells

• Neurons

– Responsible for information transmission

throughout the nervous system

• Glial cells

– Support neurons by disposing of waste products

of neurons, keeping their chemical environment

stable, and insulating them

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A Brain Myth

• Present claims suggesting there are far more glial cells than neurons seem to be a brain myth.

– No published studies support this claim.

• Not only do neurons and glial cells communicate, but glial cells communicate with one another in a separate but parallel network to the neuronal network.

The Structure of a Neuron (part 1)

• Dendrites– Include fibers that project out of the cell body, receiving

information from other neurons

• Cell body– Contains the nucleus of the cell and other biological machinery to

keep the cell alive

• Axon– Transmits messages through the neuron

• Axon terminals – Are at the end of the axon and send messages to a different neuron

The Structure of a Neuron (part 2)

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Neural Bases of Behavior

• Neurons: Basic building blocks of the nervous system

– Functions: Generate electrical activity, communicate with muscles, glands, other neurons


• Neurons: Basic building blocks of the nervous system

– Functions: Generate electrical activity, communicate with muscles, glands, other neurons

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How Neurons Communicate

• Communication within neurons is electrical.

• Communication between neurons is chemical.

• Roughly…


• Cell body (soma): Contains structures needed to keep neuron alive

• Dendrites: Collect messages from other neurons, send to cell body

• Axon: Conducts electrical impulses to neurons, muscles, glands

The Electrical Impulse: Information

from the Dendrites

• Excitatory (telling neuron to generate an

electrical impulse)

• Inhibitory (telling neuron not to generate

an electrical impulse)

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• Resting potential of cell = -70

millivolts

• Action potential: When electrically

stimulated, interior voltage shifts to

+40 millivolts


• Creating the action potential

– Electrical stimulus stimulates opening of sodium (Na+) channels, creating depolarization


• Restoring the resting potential

– Cell closes Na+ channels; potassium ions (K+)

flow out; Na+ ions are pumped out

– Absolute refractory period (cannot discharge

impulse)

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• All-or-none law

– Action potentials occur at a uniform and maximum intensity, or they do not occur at all

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The Electrical Impulse

• Myelin sheath– Insulating layer of fatty white substance that

encases the axon

– Allows electrical message to be transmitted faster within the neuron

– Responsible for distinction between brain white and gray matter

– Slows electrical impulses when damaged

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• Two types of signal transduction

– Electrical

– Chemical


• Synaptic Transmission Stages

– Synthesis

– Storage

– Release

– Binding

– Deactivation

Synaptic Communication Between

Neurons

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• Synthesis

– Neurotransmitters formed inside the

neuron


• Storage

– Neurotransmitters stored in synaptic vesicles

• Chambers located in the axon terminals

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• Release

– Action potential leads to movement of

vesicles to axon terminal surface and

release of neurotransmitters


• Binding

– Neurotransmitters bind themselves to receptor sites on receiving neuron’s membrane


• Excitatory neurotransmitters: create a graded or action potential

• Inhibitory neurotransmitters: prevents the postsynaptic neuron from firing an action potential

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Neurotransmitters, Drugs, and

Poisons

• Agonists

– Drugs and poisons that increase the activity of

one or more neurotransmitters

• Antagonists

– Drugs and poisons that decrease the activity of

one or more neurotransmitters

Neurotransmitters• Acetylcholine (ACh)

• Dopamine

• Serotonin and norepinephrine

• GABA

• Glutamate

• Peptides

– Endorphins

– Gut hormones (e.g., Somatostatin, Insulin)

Acetylcholine (ACh)

• Botulinum poison (botulin)

• Curare

• Black widow spider venom

• Deficient in Alzheimer’s disease

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Dopamine

• Dopamine systems in brain

• L-Dopa

• Antipsychotic drugs

• Amphetamine

• Cocaine

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Serotonin and Norepinephrine

• Selective serotonin reuptake inhibitors (SSRIs)

– Antidepressant drugs that work by blocking the reuptake of serotonin

– Prozac, Paxil, and Zoloft

• Selective serotonin and norepinephrine reuptake inhibitors (SSNRIs)

– Antidepressant drugs that work by blocking the reuptake of serotonin and norepinephrine

– Cymbalta, Pristiq, and Effexor

GABA and Glutamate

• Anti-anxiety drugs

– GABA 15-20% of activity in the neocortex

– Agonists for GABA

– Involved in memory and learning

• Glutamate

– Glu ≈ 75% of activity in the neocortex

– Involved in memory storage, pain perception,

and cortical processing in general

– Excessive glutamate can lead to neuron death

(e.g., stroke); deficient glutamate has been

linked to schizophrenia.

Endorphins

• Morphine and heroin

– Agonists that bind to receptor sites, thereby

increasing endorphin activity

– Trigger brain's reward centers, causing release

of dopamine

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Neurotransmitters and Some of

Their Functions

Table 2.1 Neurotransmitters and Some of Their Functions

Neurotransmitter Involved in:

Acetylcholine (ACh) Learning, memory, muscle movement

Dopamine Arousal and mood states, thought

processes, physical movement

Serotonin and NorepinephrineLevels of arousal and mood, sleep, eating

GABA (main inhibitory neurotransmitter) Lowering arousal and anxiety,

regulating movement

Glutamate (main excitatory

neurotransmitter)

Memory storage, pain perception,

strokes, schizophrenia

Endorphins Pain relief and feelings of pleasure

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• Specialized transmitter systems

– Neuromodulators (e.g. endorphins)

• Modulate the sensitivity of neurons to their specific transmitters

Effects of Drugs

• Agonists: Drugs that increase neurotransmitter activity

• Antagonists: Drugs that inhibit or decrease neurotransmitter activity

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Effects of Drugs

• Alcohol: depressant; agonist and antagonist

• Caffeine: stimulant; agonist for adenosine

• Nicotine: agonist for acetylcholine

Effects of Drugs

• Amphetamines: stimulants; increase activity of dopamine and norepinephrine

• Cocaine: blocks reuptake of dopamine and norepinephrine

Evolutionary Psychology

• Problem of adaptation to environments

• Result = evolved psychological mechanisms and behavioral strategies

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• What is evolution?

– Change over time in frequency with which genes, and characteristics they produce, occur within an interbreeding population


• Mutations

– Create genetic variations, making evolution possible

– Can be passed to offspring


• Principle of Natural Selection (Darwin)

– Characteristics more likely to be preserved if they:

• 1) increase the likelihood of survival

• 2) increase the ability to reproduce

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• Adaptation

– Products of natural selection

– Allows organisms to meet environmental

challenges to their survival


• Examples of human adaptations

– Bipedal locomotion

– Development of tools, weapons

– Social organization (hunting in groups)

– Change in brain structures

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• The lineage Homo

• Australopithecines

• Last common ancestor between the apes & us lived c 5 to 7 mya.

• Earliest members of our lineage, the Australopithecines, from c 6 to

c 2 mya.

• The Australopithecines were bi-pedal but long arms, long, curved

fingers & toe bones suggesting they were also arboreal.

• The Australo. had brains approx. same size as modern great apes.

• The Australo. were a highly adapted species in their own right.

• robustus were contemporaneous with the earliest forms of Homo.


• Early Homo

• The genus Homo is thought to have arisen from one of the gracile

Australo.forms.

• The first earliest Homo was habilis – appeared around 2 mya.

• habilis ‘handy man’ the first to use tools.

• Next was ergaster/erectus, with a further increase in brain size and

larger stature, arose around 1.8 mya.

• erectus had bigger brain, larger morph and was the first hominid to

radiate out of Africa.

• erectus appears to be the longest lived of Homo species to date – c

1.5 my’s.


• Homo sapien sapien

• ‘Out-of-Africa’ (or ‘African Eve’ hypothesis) suggests all living

humans share a recent common ancestor that lived in Africa c

100 000 to 200 000 years ago.

• This species crossed the Levant land bridge around 60 000

years ago: At this point tool construction & use diversified.

• Subsequently spread across Eurasia, into Australia, and, via the

Bering Strait, into the America’s c15 000 years ago.

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Neanderthal Ancestry

Yotova et al. “An X-Linked Haplotype of Neandertal Origin Is

Present Among All Non-African Populations,” Mol. Biol. Evol. 28

(7), 2011

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Neanderthal Ancestry

Simonti et al. science.sciencemag.org/cgi/doi/10.1126/science.aad2149

Denisovan Ancestry

Sankararaman, et al. (2016). Curr Biol

Denisovan Ancestry

• HLA antigens

– Half of the HLA alleles of modern Eurasians

represent archaic HLA haplotypes, and have

been inferred to be of Denisovan or

Neanderthal origin

• EPAS1

– Tibetans have a region of DNA, haplotype,

around the EPAS1 gene that assists with

adaptation to low oxygen levels at high altitude

(> 4000 m).

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Australopithecus Homo erectus Neandertal Homo sapiens


• Caveats

– Role of culture in behavior?

– Acknowledgement of roles of both remote and proximate (near-term) causes of behavior

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Genetic Influences on Behavior

• Genotype = genetic makeup of the

individual

• Phenotype = individual’s

observable characteristics


• Chromosome = Double-

stranded, coiled molecule of

deoxyribonucleic acid (DNA)

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• Heredity encoded in combinations of bases

adenine, thymine, guanine, and cytosine

• Genes contain bases, carry codes for protein

manufacture


• Characteristic displayed if:

– Dominant genes from both parents

– Two recessive genes

– Polygenic transmission (multiple gene pairs influence phenotype)


• Field of behavior genetics

– Study of how heredity and environment interact to influence psychological characteristics

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• Concordance

– Co-occurrence of a trait in people who are

closely related.


• Adoption Studies

– Early adoptees are compared with both biological and adoptive parents

– More similar to biological = strong influence of genes


• Twin studies

– Compare concordance rates for monozygotic (identical) and dizygotic (fraternal) twins

– If MZ twins are very alike and more so than DZ twins, genetic factors are likely

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• Heritability coefficient

– Estimates the extent to which variation in a group can be attributed to genetic factors


• Gene Manipulation

– Recombinant DNA procedures

• Enzymes cut DNA, combined with DNA from other organism, inserted into host organism

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