Study Design Content
• contribution of studies to the investigation of cognitive
processes of the brain and implications for the understanding
of consciousness including:
– studies of aphasia including Broca’s aphasia and Wernicke’s
aphasia
– spatial neglect caused by stroke or brain injury
– split-brain studies including the work of Roger Sperry and
Michael Gazzaniga
– perceptual anomalies including motion after-effect, change
blindness, synaesthesia
1
Studies on Cognitive Processes of the
Brain
 Aphasia
 Broca’s aphasia
 Wernicke’s aphasia
 Spatial Neglect
 Split-Brain studies
 Perceptual anomalies
 Motion-after effect
 Change blindness
 Synaesthesia
2
Aphasia
 The term aphasia is a general term used by clinicians to
describe individuals with a language disorder
 Neuropsychologists commonly define aphasia more
specifically to refer to a language disorder apparent in speech
(comprehension or production), writing or reading produced
by injury to brain areas specialised for these functions
 The common cause of aphasia is a stroke to a particular part
of the brain which is involved in language production or
comprehension
3
Aphasia
4
Broca’s Aphasia
 Damage to Broca’s area, in the left frontal lobe next to the motor
cortex, leads to a person having difficulty speaking, although their
ability to comprehend and understand speech is unaffected
 Speech often consists of very few words, and usually only nouns
and verbs are spoken
 Most people with Broca’s aphasia are aware of their language
difficulties and have a relatively clear understanding of their
condition
 Video clip - Individual with Broca’s aphasia
5
Wernicke’s Aphasia
 Wernicke’s aphasia is a type of aphasia in which individuals have
great difficulty in comprehending speech and speaking in a
comprehensive way
 This type of aphasia is usually a result of damage to Wernicke’s
area, located in the temporal lobe of the left hemisphere
 Unlike someone with Broca’s aphasia, speech is fluent and
grammatically correct, but what is said is incomprehendible and is
generally nonsense words and phrases
 Unlike people with Broca’s aphasia, individuals with Wernicke’s
aphasia have little awareness or understanding of their condition
6
 Video clip – Individual with Wernicke’s aphasia
Spatial Neglect
 Generally spatial neglect is an attentional disorder where an
individual fails to acknowledge anything on their left or right side
and they tend to behave as if that particular side of their world
does not exist
 This disorder is most frequently seen in stroke or accident victims
who have extensive damage to the rear part of the right parietal
lobe – this means that these individuals mostly neglect the left side
of their world
 Spatial neglect to the right side sometimes occur after similar
damage to the left side but is much less frequent and milder
7
Spatial Neglect
8
Spatial Neglect
 Spatial neglect is a complex disorder with many subtypes –
although it usually occurs in a visual sense, it may occur for other
senses such as hearing, touch or movement
 It may also be isolated to one or a combination of senses
 The extent of neglect varies between patients and depends on the
severity and exact location of the damage – some patients recover
gradually from the disorder as seen in Figure 4.40 on page 219
9
Split-Brain Studies
 Split-brain surgery involves surgically cutting the corpus callosum (and
sometimes other nerves connecting the hemispheres), effectively
severing the connection between the left and right hemispheres
 This was often used as a treatment for epilepsy as the electrical activity
in the brain which causes the problem would be able to move
throughout the brain via the corpus callosum and affect the whole brain,
often resulting in violent seizures
 Initially split-brain surgery was deemed not to have been a success as the
seizures still persisted and it was abandoned
 Later research by a famous psychologist Roger Sperry and his student
10
Ronald Myers on the effects of split-brain surgery on cats led two
American neurosurgeons to reconsider the treatment on patients – they
reasoned that some of the earlier work had failed because the connection
between the hemispheres was not complete
Split-Brain Studies
 Bogen and Vogel performed split-brain surgery on 11
epileptic patients each time cutting the corpus callosum and
some of the other nerves connecting the hemispheres
 The procedures were successful leaving the individuals
virtually seizure free and with minimal side effects
 Roger Sperry and Michael Gazzaniga performed extensive
research on these 11 patients to test the effects the split-brain
surgery had on their brain and hemisphere connection
11
Sperry and Gazzaniga
12
Sperry and Gazzaniga
 Sperry and Gazzaniga tested all 11 of the split-brain patients as well as
individuals with their corpus callosum intact
 Each participant was seated behind a screen which is used to flash a
word or picture for a fraction of a second while the individual focuses on
a black dot in the mid-point of the screen. The work or picture is flashed
to either the left or right of the black dot
 Visual information flashed to the left of the black dot is in the
participants left visual field and is therefore sent to the right hemisphere,
while visual information flashed to the right of the black dot is in the
participants right visual field and is therefore sent to the left hemisphere
 Behind the screen and hidden from view are several object such as an
13
apple, spoon and pencil – although they are hidden from view, the
participant may reach under the screen and touch them therefore
experience tactile sensation if they are able to do so
Sperry and Gazzaniga
 When an object was flashed to the screen, Sperry would ask, “What did you
see?”
 In response to images flashed to the right visual field (and sent to the left
hemisphere), the participants could name the objects but when the object was
flashed to the left visual field (and sent to the right hemisphere), the participant
could not say what they had seen and often denied anything had been flashed on
the screen other than a ‘flash of light’
 If the visual information in the right hemisphere cannot cross back into the left
hemisphere (because the corpus callosum has been severed) the participant
could not say what they had seen
 This is because the control of speech is located in the left hemisphere
 In order to be sure the participant did see the object Sperry asked the
14
participants to locate the object under the table using their left hand which they
could correctly do because their left hand is controlled by their right motor
cortex in the hemisphere that also saw the image of the object
Sperry and Gazzaniga
 It is evident that the right hemisphere had processed the
information about what the participant had seen because they
could correctly locate it using their left hand
 However, the participant could not say what the object was
because language is controlled by the left hemisphere and only the
left hemisphere could convert the information into spoken words
 This research provided indications of specialised functions by the
hemispheres as well as the role of the corpus callosum in
exchanging information between the hemispheres of the brain
15
Sperry and Gazzaniga
 The two hemispheres can compensate for the absence of a corpus
callosum and other neural connections
 Most tasks are involved in both hemispheres and although one
hemisphere may specialise in a task it does not mean that the task
is performed exclusively in that hemisphere
 Video clip - Michael Gazzaniga performing research on a split-
brain individual
16
Perceptual Anomalies
 Perception occurs when sensory information reaching the brain
is meaningfully interpreted
 The term perceptual anomaly is used to refer to an
irregularity in perception and usually involves a mismatch
between the perceptual experience and physical reality
 We will examine three examples of perceptual anomalies
involving the perception of movement (motion after-affect),
failure to see something that actually takes place (change
blindness), and a perceptual anomaly that involves unusual
experiences in one sense when another sense is stimulated
(synaesthesia)
17
Motion After-Effect
 Motion after-effect is the perceptual illusion of movement of a
physically stationary visual stimulus following exposure to visual
motion
 The stationary stimulus appears to move in the opposite direction
to the original (moving) stimulus
 It was first mentioned by philosopher Robert Addams who was
staring at a waterfall when he noticed that when he shifted his gaze
to the surrounding rocks, they appeared to move upwards –
Addams referred to this as the waterfall illusion
18
Motion After-Effect
19
Motion After-Effect
 Research indicates that eye movements and neurons in the visual
cortex specialised to detect and respond to motion are directly
involved in the illusionary effect
 Studies have also found that there are neurons in the visual system
which are sensitive to the direction of movement
 Illusions such as the motion after-effect show us that perception,
although reliable, may not always reflect reality
 Box 4.13 – Case study of akinetopsia – motion blindness, pg. 227
20
Change Blindness
 Before we talk about change blindness, lets watch a short
video
 Video clip - The Monkey Business Illusion
21
Change Blindness
 Change blindness refers to the difficulty which individuals have
in noticing large changes to visual scenes
 Research indicates that we experience a remarkable lack of
awareness of events that take place in our visual environment
 Change blindness occurs when both change is expected and
unexpected
 When it is expected, we may eventually detect the change but it
can take an astonishingly long time to do so, even for large changes
22
Change Blindness
 For change blindness to occur it has to involve some kind of
visual disruption, such as brief obstruction during an eye
movement.
 This means that change blindness is different from
inattentional blindness which is a failure to notice
something in a scene when the same scene continually
remains in view
 Video clip - Change blindness
23
Change Blindness
 American psychologist Ronald Rensnik (1998) examined whether an observer
is able to sense that a change is occurring even though they have no visual
experience of the change
 Rensink used a flicker technique where observers were shown a flicker
sequence in which an image of a real-world scene alternated with a similar
image that had been changed
 Observers pressed a button first when they were aware that something was
changing and second when they visually experienced the change
 14 of the 40 observers reported ‘feeling’ that something was changing in a large
number of trials
 The results show that some individuals have a conscious experience of change
without an accompanying visual experience
24
Synaesthesia
 Synaesthesia is a perceptual experience in which stimulation of a
particular sense elicits an additional unusual experience in another sense
- the additional experienced sense adds to the overall perception
without replacing the initial sense
 Researchers have found that synaesthesia is a real experience rather than
an imagined one and can be distinguished by a number of characteristics
It is involuntary
It is very difficult to suppress
The experience is highly vivid, memorable and consistent across time
Although consistent for each individual, the condition varies between
sufferers
 The condition tends to be one-way rather than bi-directional so if a sound
produces a taste sensation this does not mean a taste will produce a sound
sensation




25
 Video clip - Synaesthesia
Synaesthesia
 One of the most common forms of synaesthesia is
known as grapheme-colour synaesthesia and
occurs when the viewing of letters or numbers
produces the experiences of colours
 Figure 4.53 shows a common strategy used to test
grapheme-colour synaesthesia – the participant is
presented with a pattern of triangular H’s and is
asked to identify the triangle
 Most individuals have difficulty locating the triangle
but individuals with synaesthesia can often easily
locate the triangle as each letter appears as a colour
making it more easily distinguished
26
Synaesthesia
 There is still relatively little known about synaesthesia and why it is
experienced
 Some think that individuals with the condition are unusually sensitive to
external stimuli while others feel it may be a result of a breakdown in
sensory and perceptual processes
 Most psychologists agree that the brains of individuals with the
condition possess unique structural and/or functional qualities
27