Download Answers to Test Your Knowledge questions for

Answers to Test Your Knowledge questions for
Chapter 11 Learning and memory
Question 11.1
The distinction between learning and non-learning as situations associated with plasticity
is not as clear as it once was (Chapters 1, 'Introduction' and 6, 'Development'). In fact, the
distinction is becoming more grey all the time. To constitute a case of learning, the
change has to reflect environmental experience of the animal in question. Any learning
experience is associated with a memory as its base. (Additional note: It used to be argued
that learning can be characterized by the fact that any change can be reversed but even
that is being called into question now. There is some suggestion that nothing is unlearnt
but new learning simply builds on and supersedes old learning. For example, some
apparently learned fears can prove difficult to 'unlearn').
Question 11.2
Some have noted important similarities between evolution (Chapter 2, 'Integrating
explanations') and learning. Both reflect adaptation to the environment. Whereas learning
is a process of adaptation within the life of an individual animal, evolution is a process of
adaptation over generations. (Additional note: Some have compared the random
mutations that are the raw material of evolution with chance expression of behaviour that
is a basis of some learning. In the former case, some mutations are adaptive and their
bearers increase in frequency whereas others are maladaptive and hence their
representation decreases in frequency. By analogy, as will be described in more detail
shortly, some behaviour is beneficial, e.g. it leads to the gain of food and so the animal
learns to perform it and the behaviour increases in frequency. Some behaviour leads to
aversive consequences, e.g. illness, trauma) and so such behaviour tends to drop out).
Question 11.3
Each of these represents a change in behaviour in the light of experience and hence can
be characterized as learning. Each can be seen to serve the adaptation of the individual
animal to its environment.
As demonstrated in the laboratory, habituation is shown when a stimulus is repeated with
no significant consequence. No contingency is arranged between the stimulus and any
other event.
By contrast, both classical and instrumental conditioning arise in a situation where there
is a contingency between two events (as arranged by an experimenter in the case of the
laboratory situation). In classical conditioning, the contingency is between two stimuli,
e.g. bell and food, whereas in instrumental conditioning it is between behaviour and a
consequence, e.g. lever-pressing and obtaining food. Of course, the laboratory conditions
are assumed to mirror environmental events that would naturally occur in the life of an
animal.
Question 11.4
A special feature of taste-aversion learning is that learning is possible in spite of the
relatively long time (e.g. several hours) that can elapse between the taste of a food and
gastrointestinal illness. The functional significance of this is that, under natural
conditions, such a long delay might be expected following tasting food and before toxins
take effect. Thus, the system needs to be able to bridge such delays. Another special
feature is that, in a species such as the rat, it is specifically taste and smell that become
devalued in this way by virtue of their association with illness. Presumably, the
functional significance of this is that normally the wild rat would discriminate foods by
their taste and smell properties.
Question 11.5
In cognitive terms, the rat in a Skinner box might be said to form a (response) ->
(outcome) cognition of the form (press lever) -> (obtain food pellet). By extrapolation
from humans, this might be characterized as declarative learning (forming a declarative
representation). Such learning would be associated with the formation of a declarative
memory. Rats might also form a stimulus-response (S-R) association of the form (lever)(press), which would be characterized as procedural learning and would be associated
with the formation of a procedural memory. With extensive training it appears that the
weight of the S-R (procedural memory) increases relative to the declarative
representation.
Question 11.6
The homunculus ('little man in the head') was described in Chapter 7, Sensory systems'.
You might recall the term 'homunculus fallacy'. The homunculus was given such roles as
waking up the brain, pulling levers and hence organizing motor reactions. The term is
used in the pejorative sense, to indicate how behaviour could not logically be organized.
Baddeley is well aware of the dangers of the homunculus fallacy and could not be
accused of falling into this trap. None-the-less, the language that is used to describe the
role of the central executive has features that give one a feeling of déjà vu. Thus, the
central executive is said to supervise memory operations.
Question 11.7
(a) For retrograde amnesia, in the case of humans, they would need to be questioned
about known events in their life that were experienced before the trauma and their recall
noted. In the case of rats, learning can be measured before, say, electroconvulsive shock
to the brain and recall tested after shock.
(b) For anterograde amnesia, following trauma, controlled exposure to events can be
given and subsequent recall measured.
Question 11.8
Such a task would be, for example, learning to turn left in a single choice T-maze or
learning to press a lever in a Skinner-box. In each case, the task might be learned on the
basis of a straightforward stimulus-response link. Such tasks might be contrasted with,
for example, tasks that require extrapolations and detours from a normal route.
Question 11.9
Categorization, classification and definition forms a very important aspect of the study of
memory. This is particularly so when attempts are made to link memory to biological
structures. The ability of humans to recall consciously and to articulate verbally what
they recall reveals an important class of memory. Indeed, it is what most people consider
to the index of memory. Explicit memory of this type can be compared and contrasted
with implicit memories that are unavailable to conscious recall but might be revealed in
an index of behaviour, as in the case of the hidden pin.
Question 11.10
Rare individuals such as H.M. reveal the effects of human brain damage in a way that is
unavailable by any other means. Dissociations between disrupted and intact forms of
memory can be revealed in this way (as is also the for the subject Gottlieb L.). Of course,
one is unable to study in the traditional experimental way the effects of brain damage in
humans and so we rely upon unfortunate accidents of nature and the effects of brain
surgery.
Question 11.11
One line of argument is that in the case of both evolution (phylogeny) and development
(ontogeny) different memory systems appear at different stages. Thus, Tulving suggests
that, in both evolution and development, procedural memory is the first to appear.
Semantic memory is a refinement of this and, in turn, episodic memory is a specialization
of semantic memory, allowing unique episodes to be represented. At this point, you
might recall in Chapter 6, 'Development', where the development of the prefrontal cortex
was described. In primates, with increasing development an increasing range of cognitive
tasks were able to be solved. This required holding information 'on-line' in memory for
later use.
Question 11.12
One might speculate that the sight of the snakes evoked fear which triggered the release
of adrenalin, noradrenalin (NA) and corticosteroids from the adrenal gland (described in
more detail in Chapter 14, 'stress and coping'). These circulate as hormones in the blood
stream. Peripheral receptors would then have detected the elevated levels of NA and
signalled the event to the brain, where, in turn, further NA (now acting as a
neurotransmitter or neuromodulator) would be released from neurons. The NA in the
brain would act to enhance the consolidation of memories, the most potent cognition at
that time being one of snakes.
Question 11.13
Memory might be distributed in the sense that it is represented by the activity pattern in a
large number of interacting neurons. The collection ofwhich neurons are activated in the
encoding of a particular memory would be expected to be influenced by the strength of
synaptic connections between neurons. Thus, strongly connected neurons might be
expected to be excited as one, whereas neurons for which there exist weak connections
might be activated independently.
Question 11.14
If a reflex is repeatedly stimulated and a decline in response is observed, this is
suggestive of habituation as being the explanation. However, without further knowledge,
we cannot rule out other possible explanations. Habituation refers specifically to a
reduction in response to a repeated stimulus that is caused by plastic changes within the
nervous system. Specifically, in the case of habituation in Aplysia, changes occur at a
synapse within the sensory-motor pathway (see Chapter 5, Figure 5.xx and in the present
Chapter: Figure 11.2).
This needs to be distinguished from other changes that might, at least in principle, equally
give rise to a reduced response to repeated stimulation. For example, the sensory neuron
might show adaptation to repeated stimulation (see Chapter 7, 'Sensory systems- general
principles'). The muscle might show fatigue. Neither of these involve synaptic change
and neither would be termed plasticity.
Given the availability of the equipment mentioned, you could try to monitor the activity
of the sensory neuron as it is repeatedly stimulated. A decline in its activity indicates
sensory adaptation. If there is no decline under conditions in which a decrease in
amplitude of response is seen, this rules out sensory adaptation as the explanation. To
examine whether muscle fatigue could be the answer, you could try repeatedly
stimulating the motor neuron under conditions that resemble those occuring during
habituation. If the muscle shows a decrease in response this suggests muscle fatigue.
Finally, you could try artificially stimulating the sensory neuron and observing the
response of the motor neuron. If the synapse is one having the capacity to exhibit
plasticity of the kind assumed to underlie habituation, you would see a decrease in the
response of the motor neuron to repeated stimulation of the sensory neuron.
Question 11.15
According to our understanding of memory consolidation, its physical basis is in a
change in connectivity between neurons. Certain synapses are thought to be strengthened,
which involves increased local levels of protein synthesis. If a protein-synthesis inhibitor
is injected just prior to the exposure of the chick to a noxious-tasting bead, this would
impair the formation of a memory for the experience. Relative to a control chick, the
injected chick would be expected to show a greater willingness to peck at the bead.
Question 11.16
Yes. At a neural level, plasticity (Chapter 6, 'Development') refers to a changing strength
of connectivity between neurons.