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COGNITION LECTURE 4 – IMPAIRED
COGNITION
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Impairments in memory
o Amnesia
o Korsakoff’s syndrome
Impairments in attention
o Hemispatial neglect
Impaired executive functioning
o Prefrontal patients

AMNESIA OVERVIEW
Amnesia is a condition caused by brain damage in which there is severe impairment of long-term
memory
When registration or storage processes are impaired by disease or accident
Caused by disease, TBI (Traumatic Brain Injury), ABI (Acquired brain injury), bilateral stroke, and
alcohol
...
g
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)
Associated with diencephalic lesions (mammillary bodies/thalamus)
ANTEROGRADE AMNESIA
A marked impairment in the ability to remember new information learned after the onset of amnesia
(unable to form new memories)
Patient HM
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He received surgery for epilepsy that involved the removal of the medial temporal lobes
including the hippocampus
...
Most old memories
remained intact, but he had difficutly recollecting any events after his surgery
...
This shows an involvement of the medial temporal lobes (including the hippocampus)
in long-term memory
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Associated with bilateral lesions
Clive Wearing
Its transient - lasting only for a short time; impermanent
DO RETROGRADE AND ANTEROGRADE AMNESIA DEPEND ON THE SAME BRAIN REGIONS?
Smith et al (2013) assessed retrograde and anterograde amnesia in 11 patients with damage to the
media temporal lobes
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81) between the extent of anterograde

and retrograde amnesia, suggesting the same brain areas are involved
...
Typically affects chronic alcoholics with a long history of
drinking
...

There are four problems with using Korsakoff patients to study amnesia
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This can make it hard to know
whether certain past events occurred before or after the onset of amnesia
...
There is frequently damage to the
frontal lobes which can produce various cognitive deficits not specific to the memory system
...

The precise area of brain damage (and the pattern of memory impairment)varies from patient
to patient
...
Brain plasticity and the learning of compensatory strategies mean patients can
alleviate some of their memory symptoms over time

Massive confusion (confabulation) and disordered eye and limb movements
Deficit in retrograde and anterograde memory – amnesia of both forms
Immediate memory is preserved
Learning deficit can render patients incapable of all but the most habitual tasks
Mair et al
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Temporal lobe structures, including the hippocampus, were normal in these patients
...

Jernigan et al
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The Amygdala consists of several subdivisions with quite diverse functions, including emotional
regulation
The hippocampus and the fornix are important for learning
Other components of the limbic system include a strip of cortex in each hemisphere called the
cingulate gyrus, which is implicated in diverse functions, including the direction of attention
...

Fail to incorporate part of the world they do not perceive – bump into doorways, only eat items on right
side of the plate
Ignore people on the left side

A frequent feature of this syndrome is Anosognosia – unaware of the disorder
Representational neglect – Piazzo Del Duomo
The fact that some patients suffering from unilateral neglect also experience left representational
neglect, affecting their imagery and their memory performance, was first reported by Bisiach & Luzzatti
(1978), who asked two neglect patients to imagine being in the Piazza Del Duomo, a well known square
in Milan, the patients' native city, and to describe the buildings and other features around the square
...
When asked to imagine standing
at the opposite end of the square, facing the cathedral, most of the features they mentioned were ones
on the other, previously neglected, side, which was now to their right
...
Clearly knowledge of features on both sides (presumably
mostly gained before they became ill) was in their memory, but they were unable to access all of it
normally from their imagery
...
People experiencing extinction report the stimulus from only one side
...
Wiggle left finger – say left, wiggle right
finger – say right, wiggle both fingers – only say right one
HEMISPATIAL NEGLECT
Behrmann, Watt, Black and Barton (1997) – analysed eye movement in neglect patients
3 groups in his experiment: controls, neglect and hemianopic - Hemianopic refers to a visual deficit patients will show similar sort of symptoms
...
Half of their visual field, in both eyes, is impaired - one can be right hemianopic or left
hemianopic

Patients with left neglect made fewer fixations and have a shorter inspection time on the contralesional
left side
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No observable bias in controls
EXAMPLE OF HEMISPATIAL NEGLECT:
TREATMENT
There are a number of methods:
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Cognitive Training
Scanning Training
Repeated neck muscle vibrations
Mental imagery training
Video feedback training

These all have reliable improvements but they are transient (doesn’t really last)
PRISM ADAPTATION

Is a fairly new method and shows promise
...
Whilst wearing glasses the patient is required to reach for visual targets
...
The improvement lasted for at least 2 hours after prism removal and so could be useful
in rehabilitation programmes
...
2008)
Pisella et al
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Prismatic effect can be
maintained for 4 days post-adaptation on the straight ahead pointing task (blindfolded and asked to
free point ahead, 10 trials then averaged score) and the line bisection task (mark the midline on 20
horizontal lines)
Frassinetti et al
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(2002) – does have its limits – after 10 weeks effect was lost – returned to their old
ways

Artificial neglect can be induced in normal people with Prism Adaptation
...
(review, see
Michel, 2006)
IMPAIRMENTS OF EXECUTIVE FUNCTIONING
Anterior parts of the brain
FRONTAL LOBE DAMAGE
What about higher level functioning? Executive function is an umbrella term for many abilities
including: planning and organising, flexible thinking, multi-tasking, self-awareness, learning rules, social
behaviour, making decisions, motivation
Pre-frontal lobe damage (TBI) often brings about impaired executive functioning in a number of
domains
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2
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4
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Problems starting (inertia)
Perseveration
Disinhibition
Deficient self-awareness
Inflexibility

PROBLEMS STARTING (INERTIA)
Apathy, unresponsiveness, have problems initiating behaviour, needs to be prompted
Superior (above) medial damage
Patient example: only ate when food put in front of them, only initiated going to toilet and bed
(autonomous functions), yet, on questioning reported plans for Christmas, New Year, holidays but never
carried them out
...
– very debilitating
Dorsolateral Lesions
Seen as difficulty suppressing on-going activities or attention to prior stimulation
DISINHIBITION
Disinhibited behaviour – impulsive
Behavioural problems:
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Aggressive outbursts, sexual promiscuity
Inability to be guided by future consequences
Poor decision making

Orbital (basal, ventral) frontal cortex damage
DEFICIENT SELF-AWARENESS AND INFLEXIBILITY
Deficient self-awareness:
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Inability to perceive performance errors
Failure to appreciate impact on others
Empathy for others

Failure to respond normally to emotional and social reinforcers
Orbital cortex and related limbic areas
Inflexibility – concrete attitude, incapable of planning, incapable of sustaining goal-directed behaviour
SUMMARY
Impaired cognition:
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Amnesia recap
Korsakoff’s syndrome
Hemispatial neglect
o Tests
o Treatments
Prefrontal damaged patients
o executive function problems



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