Addiction and neural ageing
Addiction and neural ageing

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Glossary for SD805_2
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declarative memory


An intermediate in androgen and oestrogen biosynthesis.


A group of mental disorders characterised by progressive loss of cognitive and other intellectual functions associated with pathological ageing.

denervation supersensitivity

Increased sensitivity of the neurons of the CNS brought about by the proliferation of receptor molecules on the postsynaptic membrane following the loss of synaptic input.

Depression, the

A period in the 1930s in Western economies that was characterised by very high levels of unemployment and poverty.


A region of the body that is associated with a particular spinal nerve.


The lower layer of skin, beneath the epidermis, consisting mainly of loose connective tissue and fibroblasts, and containing nerves, vascular tissue (veins and lymphatics), hairs and sebaceous glands.

developmental psychology

A branch of psychology that sees human development as progressing in qualitative leaps or stages. This branch of psychology has mainly been concerned with childhood development but authors such as Eric Erickson have extended the analysis to the whole of the lifespan.

diabetes mellitus (types I and II)

Clinical condition in which either insulin is absent (type I, insulindependent) or in which insulin responsiveness is lost (type II, non-insulin-dependent). Characterized by the copious production of sweet urine.

dichotic listening

Listening to two different inputs simultaneously. This is a paradigm used very often to study attention where subjects listen to a series of two different things at the same time. Subjects are subsequently asked to repeat words previously presented.

differential gene expression

The expression of different sets of genes in different types of cell or at different stages of a cell’s life cycle.


Term describing cells that have become specialised into particular types.


The passive (i.e. non-energy-requiring) movement of a substance from a region where it is at a high concentration to a region where it is at a lower concentration.


A two-ring sugar, e.g. sucrose, lactose.


The ability to distinguish between two stimuli. It is measured by rewarding a response in the presence of one stimulus but not in the presence of the other and seeing whether behaviour shows a discrimination.

discriminative stimulus

A stimulus that is paired with either reward (i.e. reinforcer) availability (+) or its lack (−). An animal’s operant behaviour can be brought under the control of a discriminative stimulus such that it responds only in the presence of the reinforcer. In other words, discrimination training involves the association of a discriminative stimulus with a reinforcer.

disengagement theory

This theory suggests that older people voluntarily withdraw from society in preparation for death, and in order that society can continue to function.

disposable soma theory

A theory of the evolution of ageing and death, which suggests that organisms derive little benefit from investing resources in maintaining and repairing body tissues and thereby increasing their lifespan beyond a certain point. To do so would be inefficient as death is inevitable and resources that could have been put into reproduction would have been wasted.

disulphide bridge

An –S–S– covalent bond between two cysteine (Cys) units in a polypeptide chain, or between Cys units in different chains in the same protein.

diurnal (circadian) rhythm

Endogenous rhythmic changes, with a periodicity of approximately 24 hours, in the behaviour or physiology of animals and plants, such as the sleep/activity cycle in animals or growth movement in plants.

dizygotic twins

Non-identical twins. Two individuals that develop in one uterus from separately fertilised eggs. Also called fraternal twins.


Short for deoxyribonucleic acid. DNA is a macromolecule made up of individual units called nucleotides, and is found in all living cells and some viruses. The DNA molecule exists as a complex of two chains in an intertwined double helix. It is the carrier of genetic information that is passed on from generation to generation by replication of the DNA molecule.


One of the brain’s neurotransmitters (chemical messengers).

double aspect

The idea that mental events and brain events are two aspects of the same underlying reality.

double dissociation

The situation where a lesion at site A produces a disturbance in function X but not Y, and a lesion at site B produces a disturbance in function Y but not X.


The contribution of internal factors to motivation.


Diagnostic and Statistical Manual (of mental disorder). An American-based reference text; the ‘Bible’ of classification of psychological disorders. DSM I was first published in 1952 and has been updated several times since then. (The number, i.e. I, II, etc., denotes the edition.)


The idea that brain events and mind events are two distinct categories of existence. According to this, the mind can exist even in the absence of a physical brain.


Negative mood, e.g. depression; the opposite of euphoria. (Adjective: dysphoric.)

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