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CHAPTER 15 Learning to Remember 301
maintaining information needed for planning a course to a location and recalling
the location of objects and occurrence of events.
Multi-electrode recordings of the hippocampus made while rats were running
mazes identied hippocampal place cells and entorhinal cortex grid cells. These
cells respond when a rat is in a particular place in the maze, with dierent cells
activated by dierent places in the maze. Other types of cells include boundary,
head direction, and speed cells.
When the rats slept after maze training sessions, their hippocampal place and grid
cells and cortical neurons red in the same pattern and sequence as when origi-
nally traversing the maze, though the time frame was compressed. Place cells may
have an important role in episodic memory where they contain information about
the spatial context in which an event took place.
Focusing on synaptic plasticity
in implicit memory
The amygdala provides input to the hippocampus for emotional content in epi-
sodic memories. In addition, the amygdala is essential for fear conditioning. In the
formation of conditioned fear memory, synapses in the amygdala undergo LTP
that is proposed toplay a role in encoding the fear memory.
Like hippocampal dependent declarative memory, the amygdala is important for
forming long-term memory and the memory probably isn’t stored there. The rep-
resentation of stimuli that activate the amygdala are thought to occur primarily in
the prefrontal cortex, most likely in the orbitofrontal cortex.
LTP has also been demonstrated in procedural memory. The striatum is the input
region of the basal ganglia. Striatal projection neurons integrate glutamatergic
excitatory inputs from the cortex and thalamus with dopamine inputs and can
undergo both LTP and LTD. Research has shown correlative and causal links
between striatal plasticity and procedural learning. This plasticity likely occurs
with learning to encode new skills and habits.
LTD occurs in the cerebellar cortex at excitatory synapses between parallel bers
and Purkinje neurons. This is induced by co-activation of parallel bers and a
climbing ber. The eect is a decreased responsiveness to the glutamate released
by the parallel bers. This synaptic plasticityhas been considered as a critical cel-
lular mechanism for procedural learning. Research studies have shown that cal-
cium, protein kinases, and a decrease in synaptic AMPA receptors are involved in
cerebellar LTD.
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302 PART 3 Understanding Perception and Cognition
Memory retrieval
Information can be retrieved from long-term memory in four ways:
»
Recall
»
Recollection
»
Recognition
»
Relearning
These dier in the nature of the cue or prompt used to trigger the retrieval. Fol-
lowing retrieval, a previously consolidated memory can become labile or change-
able through reactivation of the memory trace. After a memory has been retrieved
and reactivated, its content can be reconsolidated through a process that enables
the updating of the memory through exposure to current stimuli and restabilizing
of the memory.
Comparing computer versus
animal memory
The human brain doesn’t work like computers. In computers, memories are stored
data strings without intrinsic meaning, until the strings are combined with infor-
mation that allows them to be interpreted according to rules stored elsewhere.
Memory in brains is a change in the neural biochemistry and architecture, such
that the processing chain from stimulus to response operates dierently. The
neural circuits that originally processed stimuli become active in recreating real-
ity, which includes many stimuli, the state of the brain at that time, and aspects
of the behavioral output.
Forgetting It: Amnesia and Other
Memory Loss
Humans can lose a memory by two dierent processes: forgetting the memory or
failing to retrieve the memory. Practically, distinguishing between these two pro-
cesses can be dicult.
In forgetting, the memory is lost because the synaptic modications underlying
the memory are altered or the neurons that instantiate the memory become inac-
tive or die. A memory may exist, however, but be temporarily irretrievable, as
many students have noted. Often, you’re able to retrieve the memory because of
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CHAPTER 15 Learning to Remember 303
some property of your environment is similar to the initial situation in which the
memory was created. This emphasizes the re-creational aspects of memory.
These sections focus on the process by which memory is lost in the clinical disor-
der called amnesia and after damage to the brain.
Losing yourself in amnesia
A common soap opera plot involves a character losing their memory and interact-
ing with other characters in a completely new way. This sort of amnesia actually
does occur, but it’s typically temporary. The cause may be brain ischemia (oxygen
and nutrient deprivation) from a vascular incident or a blow to the head. This sort
of memory loss may include complete loss of episodic information from the pres-
ent back to some point in the past, as well as semantic loss over a similar period.
Semantic and procedural information from early life may remain intact.
Electroconvulsive therapy also produces memory loss. The pattern tends to involve
a four- to six-month retrograde loss and a month or two of anterograde inability
to form new memories. In many cases, most of the retrograde lost memories
return. This gives a clue about the memory consolidation process, which must
take place over several months.
Damaging the hippocampus or frontal lobe
In the movie Groundhog Day, Phil wakes up every morning with memories intact,
but doomed to repeat the same scenario. This is the opposite of H.M., who men-
tally relived every day anew without any memory of the people or events since his
surgery. Damage to the hippocampus and nearby temporal lobe interferes with
memory formation and can compromise the ability to retain recently learned
information and recall contextually rich events. Stress, physical or emotional
trauma, and pathologies can reduce neuroplasticity in the hippocampus and pre-
vent learned adaptation to new information.
Damage to the dorsolateral prefrontal cortex disrupts working memory and,
therefore, the ability to form episodic memories.
The amygdala produces representation of situations that are likely to have nega-
tive consequences, particularly for social situations. The interaction between the
amygdala and the orbitofrontal cortex (a region within the ventromedial prefron-
tal cortex) allows learning of new contingencies that are predictive of negative
consequences. Damage to this region can cause people to do risky or inappropriate
things because they have no fear of negative consequences.
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304 PART 3 Understanding Perception and Cognition
This eect is illustrated in the famous case of Phineas Gage, a railroad worker who
suered damage to the ventromedial prefrontal cortex. The injury transformed
Gage from a normal, reliable, and responsible crew foreman to an irresponsible
gambler who swore constantly.
Examining Alzheimer’s disease
Alzheimer’s disease (AD) is the most common form of dementia. AD likely devel-
ops from multiple factors, including genetics, lifestyle, and environment. Muta-
tions in amyloid precursor protein (APP) and presenilin can cause inherited forms
of AD. Variants in the apolipoprotein E4 gene increase the risk of AD with the
greatest known impact.
The rst symptom of AD is memory loss, particularly episodic and spatial mem-
ory. In the early stages of AD the cholinergic neurons (that use acetylcholine) in
the basal forebrain, which project to the hippocampus and entorhinal cortex, have
impaired function or undergo degeneration. Cholinergic input is a critical part of
hippocampal physiology, and the loss of these inputs may compromise the ability
to encode episodic and spatial memories.
AD involves the accumulation of protein aggregates in the brain. The leading
candidates for the cause of AD are amyloid beta and tau. Amyloid beta is a frag-
ment of APP that is involved in neuronal development. The misfolded amyloid
beta proteins form amyloid plaques outside neurons— known as senile plaques.
Aggregated amyloid beta is toxic to neurons.
In AD, tau accumulates inside neurons forming neurobrillary tangles. Tau’s nor-
mal function is to stabilize microtubules in the cell cytoskeleton, and tau has been
shown to associate with mitochondria and synaptic vesicles. Tau is regulated by
phosphorylation, and in AD tau becomes hyperphosphorylated, altering its
functions.
Cholinergic neurons are particularly susceptible to the damage in AD. Several
medications used to treat AD symptoms act by increasing acetylcholine levels or
ecacy by inhibiting acetylcholinesterase, which is the enzyme that breaks down
acetylcholine. Another drug used to treat AD is memantine, which is an NMDA
receptor antagonist.
Recently, the FDA approved biologics that have been developed for the treatment
of AD.Anti-amyloid monoclonal antibodies are the rst disease-modifying thera-
pies for AD.They may slow cognitive decline by decreasing amyloid beta–induced
disease progression in AD.
The course of AD proceeds from episodic and spatial to semantic memory loss,
and then nally to large-scale degeneration of neurons throughout the brain.
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CHAPTER 15 Learning to Remember 305
Declining health is usually caused by the disruption of body function regulation
carried out by subcortical brain areas.
Improving Your Learning and Memory
Classical learning theory shows that repetition, particularly when associated with
reinforcement, causes behaviors to be retained, including the ability to recapitu-
late facts in semantic memory. Less well understood, because we have no animal
model for semantic memory, is the dierence between deep learning and shallow
learning. Deep learning is the linkage of new information to multiple levels of
one’s already-existing semantic Here we discuss techniques and behaviors that
are proposed to enhance memory.
Studying hard versus studying well:
Schedules
Repetition results in learning, but some ways of conducting repetition while
studying are more eective than others. Two major practices can improve learn-
ing for a given amount of time:
»
Deep content association: Deep content association refers to linking new facts
to multiple aspects of your knowledge base. For example, the shallow method
to study the Battle of Hastings would be to memorize facts about locations,
people, and timing. A deeper way to learn would be to simulate the battle in
your mind or with a map or computer program. If you considered the
situations the commanders faced and their resources and decisions, you
would be much more likely to remember the progress of the battle.
»
Spaced practice: Also known as spaced repetition or the spacing eect, it’sa
learning strategy where practice is broken up into a number of short sessions
over a longer period of time. Cramming is ineective for long-term retention.
Learning is more eective when spread out over time. As with distributed
learning, part of this may involve context. If you practice learning at multiple
times, in multiple contexts, learning will be deeper and you’ll be more likely to
recall what you’ve learned.
Traveling the path to better memory
Individuals have known about specic techniques to help them memorize lists
since ancient times. The most well-known is called the journey method or method
of loci. In this method, the person imagines walking a familiar route and
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306 PART 3 Understanding Perception and Cognition
associating a word on the list to be remembered with specic landmarks on the
route. A memory palace is an imaginary building where you make a journey in the
same order through the rooms where you’ve stored mnemonic images.
This is an example of a deep association because the route the person uses is
familiar, and they can remember the entire route. The technique creates a link
between each landmark and an item on the list, so that the items to be remem-
bered are embedded in the past, current, and future locations to be encountered
that already exist in memory.
This technique appears to use regions of the hippocampus that have to do with
spatial learning. Multi-electrode recordings in rats have shown that much of their
hippocampal resources are devoted to representation of place in spatial naviga-
tion. The journey method links a list to be learned to an already learned spatial
representation. The hippocampus probably originally evolved primarily for learn-
ing in spatial navigation, and its role in episodic memory evolved later from that.
Enhancing memory through
training and exercise
Even though many studies show that for healthy individuals, brain-training can
improve performance on the trained tasks, little evidence suggests that training
enhances performance on distantly related tasks or improves cognitive
performance. However, observational studies show thatpeople who do mentally
stimulating activities may have a lower risk of cognitive decline and dementia.
Other studies show that brain training using cognitive apps can improve cognitive
performance and processing speed in older adults.
Evidence suggests that both acute and chronic exercise can improve memory
function. Aerobic exercise increases blood ow to the brain. Exercise can also
enhance neuroplasticity. It leads to increases in endogenous cannabinoids and
opioids that may modulate memory. Studies have shown that muscle activity can
release myokines such as irisin into the circulation, which may increase levels of
neurotrophic factors such as BDNF, that can enhance synaptic plasticity.
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CHAPTER 16 The Frontal Lobes and Executive Motor Control 307
Chapter16
The Frontal Lobes and
Executive Motor Control
I
nsects and invertebrates perform complex behaviors like ying without a
neocortex — and they get along just ne. Their subcortical areas are good
enough for controlling what they need to do. But for humans, that’s not
good enough.
In humans, a lot of the brain serves the purpose of allowing us to act, and to
decide how to act, intelligently— based on previous experiences and current situ-
ations. Without a neocortex, the number of possible behaviors we could perform,
and contingencies that we base our decisions to act, are very limited.
The frontal lobe controls the complex plans you need to make for doing all kinds
of things, every day. Hitting tennis balls and climbing a ladder to paint the ceiling
are behaviors that require a frontal lobe to execute. And the human frontal lobe,
particularly on the left side, allows you to have not only thoughts, but thoughts
about thoughts, and thoughts about thoughts about thoughts. This chapter looks
at how the human brain allows you to act in complex ways depending on your
goals, experience, and self-awareness.
IN THIS CHAPTER
»
Acting reexively or consciously
»
Processing experience and
environment in the frontal lobes
»
Making it happen with the basal
ganglia
»
Managing muscle movements and
sequences
»
Looking into mirror neurons
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308 PART 3 Understanding Perception and Cognition
Comparing Reexes versus Conscious or
Goal-Generated Action
Flight is one of the most complex animal behaviors. Wing movements must
account for obstacles, wind and wind changes, air pressure, current altitude, and
direction. Yet many primitive animals, such as insects, y quite well. The intelli-
gence necessary for ight in invertebrates is embedded in their genome, which
learned or adapted over billions of years of evolution.
Insect ight demonstrates that complex behaviors don’t necessarily require large
brains. Large brains are required for complex planning, maintaining status and
surviving in large social groups. But some insects— such as ants— exist in large
social groups called castes. In ants, castes include queen, worker, drone, and prin-
cess (but no social status within each caste). So membership in large social groups
also doesn’t require a large brain.
The crucial dierence between insect and mammalian social groups is that insect
social groups are composed of only a few castes. An insect’s behavior is almost
completely specied by a few types of responses to stimuli as a function of its
caste. But many mammalian social groups consist of individuals, each of which
has a specic identity and social rank. Interactions between mammals in a social
group depend on things like their mutual rank, which other individuals are pres-
ent and their ranks, and on the outcomes of previous encounter-experiences of all
these individuals. This is particularly true for primates, who maintain separate,
simultaneous male and female social hierarchies, with the male hierarchies in a
constant status of ux due to dominance contests.
Large brains are associated with the need for complex representations of reality.
A mammal can be in the exact same situation today — as represented by the
senses— as yesterday; however, the appropriate behavior today could be quite
dierent from what it was yesterday, depending on the memory of what was
observed to happen yesterday between other members of the troop.
The need for this type of situational intelligence drove hominid evolution far
beyond the brain size needed for a complex behavior such as ight. It required the
ability to enhance sensory processing to detect subtle facial expressions, posture
changes, and cues from vocalization. It required episodic memory (refer to
Chapter15) for the outcomes of specic encounters and subtle changes in vocal-
izations that conveyed, or sometime hid, information about status.
The neocortex, particularly the frontal lobes, allowed a much more nuanced
control of behavior than was possible from limbic stimulus-response instinctive
control. The representation of complex contingencies in the brain allowed
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CHAPTER 16 The Frontal Lobes and Executive Motor Control 309
complex planning and tool making. Producing experience-dependent vocalization
led to language, sophisticated cooperation, and teaching the young. The large
contingency-representing human brain also produced blung, lying, deceit,
altruism, and spiritual explanations for reality. The following sections describe
how the neocortex built on evolutionary older vertebrate brain structures for the
control of movement and behavior.
Turning ideas and goals into action
The brain is designed not by engineers, but by evolution via natural selection. The
nervous system consists of a lot of hacks— repairs, patches, and shortcuts in a
large system that evolved modications to deal with an unforeseen contingencies
with causing the least amount of disruption to the rest of the system.
Hacks work best in modular hierarchical systems because this structure limits the
eects of the hack inserted to deal with the unforeseen contingency on other sys-
tems. For example, an ancient evolutionary hack is to use the reex of stepping
when falling forward to generate walking. Many brain functions are implemented
by neural circuits no engineer would design but that were adapted for new uses
from existing circuits.
Lizards and frogs can generate all their locomotive behaviors without a neocortex
by using the basal ganglia, cerebellum, and spinal pattern generators and reexes.
When mammals evolved a neocortex, they didn’t throw this older neural circuitry
away and develop a new system. Instead, mammals co-opted the less complex
systems they inherited by controlling them at a higher level, based on more com-
plex contingencies and learning.
For example, monkey A may notice a rival coming into its area. Monkey A doesn’t
want to confront monkey B because he has an ally who isn’t around now. Monkey
A doesn’t want to ee or give evidence of submission. Monkey A’s best strategy is
to use deceit and leave quickly but without showing fear. Monkey A’s frontal lobes
are generating all these calculations, using the monkey’s subcortical gait control
systems to carry out the actions of his limbs, moving it away from monkey B.The
subcortical limbic systems may be prompting monkey A to ee hurriedly from the
threat, but he doesn’t.
Humans in particular have generated novel behaviors. Examples are odd gaits like
skipping and gait patterns in dancing, or dexterous hand use for making and
using tools and sign language. These behaviors have led to the development of a
nearly complete cortical circuit for control of the limbs that largely bypasses more
subcortical control used by other mammals.
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310 PART 3 Understanding Perception and Cognition
Just anterior to the primary motor cortex are two areas:
»
Supplementary motor area: Located in the medial frontal cortex, anterior to
the primary motor cortex
»
Premotor cortext: Also known as Broadmann area 6, located in the lateral
frontal cortex anterior to primary motor cortex
Abstract goals represented in the prefrontal cortex activate the basal ganglia and
either the supplementary motor area and cerebellum or the premotor cortex and
parietal lobe for generating action sequences. These areas, in turn, activate the
primary motor cortex to control muscles directly (refer to Chapter 8 for more
details). These areas allow new and learned capabilities, such as hitting a tennis
backhand or building a bookcase.
Representing actions at multiple levels
Most goals can be reached in many ways. If you want ice cream, you can drive to
the grocery store or to an ice cream parlor or walk or cycle to those places; you can
ask your neighbor if they have any; or you can make it yourself if you have an ice
cream maker and the ingredients.
The goal of wanting ice cream is very abstract, probably represented in lateral
prefrontal cortex with inputs from hunger mechanisms, emotion, and memory.
Evidence suggests that this goal may simultaneously activate many of the possible
ways of achieving it. The activation of goal resolution paths generates the sub-
goals required for each of them. Your frontal lobe has to sort out the requirements
for the subgoals as well.
The real hallmark of frontal lobe engagement is what happens when the planned
procedure doesn’t work. If you planned to cycle to the grocery store but your bike
has a at tire, is it now more appropriate to x the tire or try to get to the store
another way? Your frontal lobes are constantly doing all these calculations for all
your goals. Much of this is unconscious, and much of it depends on learning and
experience that evolution couldn’t have programmed.
Deciding How to Do It: The Frontal Lobes
Play is a nearly universal behavior in young mammals. Play is practice for learning
behaviors. Predator mammals play at catching and knocking down prey, whereas
prey animals practice escaping. Mammals also explore, establish, and defend
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