UNIVERSITY OF SOUTH AFRICA (UNISA)
College of Human Sciences, Department of Psychology
⋄
PORTFOLIO ASSESSMENT
Assessment 3 — 2026
⋄
Module Code: PYC4813
Module Name: Cognitive Neuroscience
Assessment: Assessment 3: Portfolio Assessment
Due Date: 29 October 2026
Unique Number: 665432
Submitted in partial fulfilment of the requirements for Cognitive Neuroscience (PYC4813)
at the University of South Africa.
,UNISA | PYC4813 Portfolio Assessment 3
Question 1: MRI versus PET and Hypothesised Findings
Question
Outline why the neuropsychologist chose to use an MRI by comparing and contrasting it to a PET
scan keeping the purpose of neuroimaging in mind. Hypothesize what the neuroanatomical MRI
findings would look like if Thabo’s poor language expression was due to a tumour or brain damage.
1.1 The purpose of neuroimaging in this assessment
In neuropsychological practice, imaging is rarely used to diagnose a condition on its own. Its
main job is to establish whether an identifiable structural or metabolic abnormality could ac-
count for the cognitive and behavioural picture, to localise that abnormality, and to relate it to
the pattern of test performance (Lezak et al., 2012; Sadek & Hammeke, 2002). Imaging tech-
niques are commonly divided into structural methods, which show anatomy, and functional
methods, which show metabolism or neural activity (Liu et al., 2015). Thabo’s referral raised
exactly this question. His language difficulties, social withdrawal and rigidity could have come
from acquired brain damage, or from a neurodevelopmental condition with an essentially nor-
mal brain structure. The scan therefore had to rule out lesions, tumours and traumatic injury,
including damage along the auditory pathway, before the psychometric findings could be inter-
preted as neurodevelopmental.
1.2 Comparing and contrasting MRI and PET
Both techniques are tomographic, meaning they build up cross-sectional images of the living
brain, and both are non-invasive in the sense that no surgery is needed. Both can be used to
relate brain findings to behaviour, and they can be combined in hybrid PET/MRI systems (Liu
et al., 2015). They differ in what they measure, how they measure it and what they cost the
patient. Table 1 sets out the main contrasts.
1.3 Why MRI was the appropriate choice
The question Thabo’s case posed was structural. The neuropsychologist needed to know whether
the brain looked intact, and MRI is the better tool for that because of its fine resolution of
Page 1 of 17
, UNISA | PYC4813 Portfolio Assessment 3
Table 1: MRI compared with PET in a neuropsychological referral
Feature MRI (structural) PET
What it shows Detailed anatomy: grey matter, white Metabolic activity or receptor bind-
matter, ventricles, lesions, tumours, ing, usually of glucose or a ligand
atrophy
Mechanism Strong magnetic field and radio Injected radioactive tracer; gamma
waves; no radiation rays are detected after positron de-
cay
Spatial resolution High, roughly one millimetre Lower, several millimetres
Temporal resolution Structural scans are static; fMRI Slow, minutes, because the tracer
tracks change over seconds must accumulate
Safety and access No ionising radiation, widely avail- Ionising radiation, needs a cyclotron
able, relatively cheaper and tracer, expensive and scarce
Typical clinical use Tumours, stroke, trauma, demyelina- Dementia, epilepsy foci, tumour
tion, malformations metabolism, receptor research
grey and white matter and its sensitivity to lesions, tumours and old injury. PET would have
added little. A normal or mildly abnormal metabolic pattern in an adult with suspected autism
would not be specific enough to confirm or exclude a diagnosis, and it would have exposed
a healthy 29-year-old to ionising radiation and a much higher cost without answering the re-
ferral question. Sadek and Hammeke (2002) note that functional techniques need to be inter-
preted cautiously, because their findings depend heavily on task design and on the limits of
the method. MRI also allowed the clinician to examine the auditory pathway, which mattered
because Thabo’s delayed speech onset made a hearing-related cause a live possibility.
1.4 Hypothesised MRI findings if a tumour or brain damage were responsible
Thabo’s problem is mainly one of expression and abstract verbal understanding, so the regions
of interest are the perisylvian language areas of the left hemisphere. These are Broca’s area in
the posterior inferior frontal gyrus (Brodmann areas 44 and 45), which supports speech pro-
duction and grammar, Wernicke’s area in the posterior superior temporal gyrus, which sup-
ports comprehension, and the arcuate fasciculus that connects them (Kolb & Whishaw, 2021).
Damage to the left frontal region would be expected to give effortful, simplified, non-fluent
speech, which resembles Thabo’s notably simplistic speech on the surface.
If a tumour were the cause, the MRI would be expected to show a space-occupying lesion in
or near the left inferior frontal gyrus or insula. On T1-weighted images it would typically ap-
pear darker than surrounding tissue, and on T2 and FLAIR sequences it would appear bright. A
higher-grade tumour would usually enhance after gadolinium contrast. Surrounding vasogenic
oedema would appear as a bright rim in the white matter, and mass effect would show as ef-
Page 2 of 17
College of Human Sciences, Department of Psychology
⋄
PORTFOLIO ASSESSMENT
Assessment 3 — 2026
⋄
Module Code: PYC4813
Module Name: Cognitive Neuroscience
Assessment: Assessment 3: Portfolio Assessment
Due Date: 29 October 2026
Unique Number: 665432
Submitted in partial fulfilment of the requirements for Cognitive Neuroscience (PYC4813)
at the University of South Africa.
,UNISA | PYC4813 Portfolio Assessment 3
Question 1: MRI versus PET and Hypothesised Findings
Question
Outline why the neuropsychologist chose to use an MRI by comparing and contrasting it to a PET
scan keeping the purpose of neuroimaging in mind. Hypothesize what the neuroanatomical MRI
findings would look like if Thabo’s poor language expression was due to a tumour or brain damage.
1.1 The purpose of neuroimaging in this assessment
In neuropsychological practice, imaging is rarely used to diagnose a condition on its own. Its
main job is to establish whether an identifiable structural or metabolic abnormality could ac-
count for the cognitive and behavioural picture, to localise that abnormality, and to relate it to
the pattern of test performance (Lezak et al., 2012; Sadek & Hammeke, 2002). Imaging tech-
niques are commonly divided into structural methods, which show anatomy, and functional
methods, which show metabolism or neural activity (Liu et al., 2015). Thabo’s referral raised
exactly this question. His language difficulties, social withdrawal and rigidity could have come
from acquired brain damage, or from a neurodevelopmental condition with an essentially nor-
mal brain structure. The scan therefore had to rule out lesions, tumours and traumatic injury,
including damage along the auditory pathway, before the psychometric findings could be inter-
preted as neurodevelopmental.
1.2 Comparing and contrasting MRI and PET
Both techniques are tomographic, meaning they build up cross-sectional images of the living
brain, and both are non-invasive in the sense that no surgery is needed. Both can be used to
relate brain findings to behaviour, and they can be combined in hybrid PET/MRI systems (Liu
et al., 2015). They differ in what they measure, how they measure it and what they cost the
patient. Table 1 sets out the main contrasts.
1.3 Why MRI was the appropriate choice
The question Thabo’s case posed was structural. The neuropsychologist needed to know whether
the brain looked intact, and MRI is the better tool for that because of its fine resolution of
Page 1 of 17
, UNISA | PYC4813 Portfolio Assessment 3
Table 1: MRI compared with PET in a neuropsychological referral
Feature MRI (structural) PET
What it shows Detailed anatomy: grey matter, white Metabolic activity or receptor bind-
matter, ventricles, lesions, tumours, ing, usually of glucose or a ligand
atrophy
Mechanism Strong magnetic field and radio Injected radioactive tracer; gamma
waves; no radiation rays are detected after positron de-
cay
Spatial resolution High, roughly one millimetre Lower, several millimetres
Temporal resolution Structural scans are static; fMRI Slow, minutes, because the tracer
tracks change over seconds must accumulate
Safety and access No ionising radiation, widely avail- Ionising radiation, needs a cyclotron
able, relatively cheaper and tracer, expensive and scarce
Typical clinical use Tumours, stroke, trauma, demyelina- Dementia, epilepsy foci, tumour
tion, malformations metabolism, receptor research
grey and white matter and its sensitivity to lesions, tumours and old injury. PET would have
added little. A normal or mildly abnormal metabolic pattern in an adult with suspected autism
would not be specific enough to confirm or exclude a diagnosis, and it would have exposed
a healthy 29-year-old to ionising radiation and a much higher cost without answering the re-
ferral question. Sadek and Hammeke (2002) note that functional techniques need to be inter-
preted cautiously, because their findings depend heavily on task design and on the limits of
the method. MRI also allowed the clinician to examine the auditory pathway, which mattered
because Thabo’s delayed speech onset made a hearing-related cause a live possibility.
1.4 Hypothesised MRI findings if a tumour or brain damage were responsible
Thabo’s problem is mainly one of expression and abstract verbal understanding, so the regions
of interest are the perisylvian language areas of the left hemisphere. These are Broca’s area in
the posterior inferior frontal gyrus (Brodmann areas 44 and 45), which supports speech pro-
duction and grammar, Wernicke’s area in the posterior superior temporal gyrus, which sup-
ports comprehension, and the arcuate fasciculus that connects them (Kolb & Whishaw, 2021).
Damage to the left frontal region would be expected to give effortful, simplified, non-fluent
speech, which resembles Thabo’s notably simplistic speech on the surface.
If a tumour were the cause, the MRI would be expected to show a space-occupying lesion in
or near the left inferior frontal gyrus or insula. On T1-weighted images it would typically ap-
pear darker than surrounding tissue, and on T2 and FLAIR sequences it would appear bright. A
higher-grade tumour would usually enhance after gadolinium contrast. Surrounding vasogenic
oedema would appear as a bright rim in the white matter, and mass effect would show as ef-
Page 2 of 17
