UNIVERSITY OF SOUTH AFRICA
College of Human Sciences | School of Psychology
⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄⋄
PYC4813: Cognitive Neuroscience
Assessment 3: Portfolio Assessment | 2026
⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄⋄
PYC4813
Module Code:
Cognitive Neuroscience
Module Name:
Neuropsychological Case Study: Thabo
Assessment Topic:
Assessment 3 (Portfolio)
Assessment Number:
665432
Unique Number:
29 October 2026
Due Date:
70
Total Marks:
Submitted in partial fulfilment of the requirements for Cognitive Neuroscience, UNISA 2026
,UNISA | PYC4813 Portfolio Assessment 3
Question 1: Neuroimaging, MRI and 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.
Neuroimaging in neuropsychological assessment relates test performance and behaviour to
the structure and function of the living brain, so that a lesion, degenerative process or injury
can be confirmed or excluded before a developmental explanation is accepted (Kolb & Whishaw,
2021). Thabo’s referral raised exactly this problem, because his language and social difficulties
could in principle reflect acquired damage as readily as a neurodevelopmental condition.
1.1 Why neuroimaging was used in this case
Imaging serves three purposes in a neuropsychological assessment. First, it screens for struc-
tural pathology such as tumours, vascular lesions, traumatic injury, hydrocephalus and atrophy,
which would change the clinical picture and sometimes demand urgent medical management.
Second, it localises any abnormality so that the pattern of test deficits can be checked against
the affected brain region. Third, it corroborates or challenges the psychometric findings, so
that the final formulation rests on converging evidence and not on test scores alone (Lezak et
al., 2012).
Thabo’s history contains delayed speech onset, poor oral expression and difficulty with verbal
learning, but no reported head injury, seizures or neurological illness. The neuropsychologist
therefore needed to rule out neurological damage before attributing his difficulties to a devel-
opmental condition. A normal scan does not diagnose autism spectrum disorder, because no
imaging biomarker for the condition has been validated for clinical use (Lord et al., 2020). It
does narrow the differential diagnosis in a way that behavioural testing cannot, and a negative
result redirects the formulation toward a neurodevelopmental explanation.
1.2 Comparing and Contrasting MRI and PET
MRI and PET both generate three-dimensional images of the intact living brain without surgery,
and both are used in diagnosis and research. They differ in what they measure. MRI places the
person in a strong magnetic field and uses radio-frequency pulses to alter, and then record, the
behaviour of hydrogen nuclei in tissue water, which produces detailed images of grey matter,
Page 2 of 18
, UNISA | PYC4813 Portfolio Assessment 3
white matter and cerebrospinal fluid (Gazzaniga et al., 2019). PET requires an injected, short-
lived radioactive tracer, most often fluorodeoxyglucose labelled with fluorine-18, and detects
the paired gamma photons produced when positrons from the tracer meet electrons. It there-
fore maps regional glucose metabolism or receptor binding (Raichle & Mintun, 2006).
Table 1: Comparison of MRI and PET in relation to Thabo’s referral question
Aspect MRI PET
Physical basis Nuclear magnetic resonance of hydro- Detection of gamma photons re-
gen protons in a magnetic field leased by a radioactive tracer
Primary informa- Anatomy: tissue structure, lesions, Physiology: regional glucose
tion volume and white matter integrity metabolism, blood flow or receptor
(functional MRI adds an indirect binding
blood-oxygen signal)
Spatial resolution Roughly a millimetre or finer Several millimetres
Safety No ionising radiation, so scans can be Radiation dose from the tracer, which
repeated limits repeat scanning
Practicalities Widely available, no tracer needed, Needs tracer production and a spe-
but noisy and confining cialised scanner, so costlier and
scarcer
Fit to the referral Directly shows whether a lesion, tu- Can show abnormal metabolism but
question mour or injury is present cannot identify its structural cause
The justification for choosing MRI follows from the referral question. The neuropsychologist
needed to know whether neurological damage was present, which is a structural question, and
MRI answers it with the highest spatial resolution and tissue contrast. MRI also avoids ionising
radiation, which matters for a young adult with no suspected degenerative disease. The same
scan allowed the auditory pathway to be inspected, which supported the later exclusion of a
hearing deficit. PET would be considered where a structural scan is normal but a degenerative
process such as early Alzheimer’s disease is suspected, since metabolic change can precede
visible atrophy. That scenario does not fit a 29-year-old with a lifelong developmental history.
A PET scan would also have added cost and radiation exposure without addressing the struc-
tural question (Kolb & Whishaw, 2021).
1.3 Expected MRI findings if a tumour or brain damage caused the poor language expression
Expressive language depends mainly on the left hemisphere in most right-handed people. Broca’s
area in the posterior left inferior frontal gyrus (Brodmann areas 44 and 45), the adjacent left
precentral gyrus and anterior insula support speech planning and production. The arcuate fas-
ciculus connects them with the posterior superior temporal region associated with Wernicke’s
area (Hickok & Poeppel, 2007). A lesion that produced Thabo’s poor expression would most
probably sit in this left frontal and perisylvian network or in its connecting white matter.
Page 3 of 18
College of Human Sciences | School of Psychology
⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄⋄
PYC4813: Cognitive Neuroscience
Assessment 3: Portfolio Assessment | 2026
⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄⋄
PYC4813
Module Code:
Cognitive Neuroscience
Module Name:
Neuropsychological Case Study: Thabo
Assessment Topic:
Assessment 3 (Portfolio)
Assessment Number:
665432
Unique Number:
29 October 2026
Due Date:
70
Total Marks:
Submitted in partial fulfilment of the requirements for Cognitive Neuroscience, UNISA 2026
,UNISA | PYC4813 Portfolio Assessment 3
Question 1: Neuroimaging, MRI and 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.
Neuroimaging in neuropsychological assessment relates test performance and behaviour to
the structure and function of the living brain, so that a lesion, degenerative process or injury
can be confirmed or excluded before a developmental explanation is accepted (Kolb & Whishaw,
2021). Thabo’s referral raised exactly this problem, because his language and social difficulties
could in principle reflect acquired damage as readily as a neurodevelopmental condition.
1.1 Why neuroimaging was used in this case
Imaging serves three purposes in a neuropsychological assessment. First, it screens for struc-
tural pathology such as tumours, vascular lesions, traumatic injury, hydrocephalus and atrophy,
which would change the clinical picture and sometimes demand urgent medical management.
Second, it localises any abnormality so that the pattern of test deficits can be checked against
the affected brain region. Third, it corroborates or challenges the psychometric findings, so
that the final formulation rests on converging evidence and not on test scores alone (Lezak et
al., 2012).
Thabo’s history contains delayed speech onset, poor oral expression and difficulty with verbal
learning, but no reported head injury, seizures or neurological illness. The neuropsychologist
therefore needed to rule out neurological damage before attributing his difficulties to a devel-
opmental condition. A normal scan does not diagnose autism spectrum disorder, because no
imaging biomarker for the condition has been validated for clinical use (Lord et al., 2020). It
does narrow the differential diagnosis in a way that behavioural testing cannot, and a negative
result redirects the formulation toward a neurodevelopmental explanation.
1.2 Comparing and Contrasting MRI and PET
MRI and PET both generate three-dimensional images of the intact living brain without surgery,
and both are used in diagnosis and research. They differ in what they measure. MRI places the
person in a strong magnetic field and uses radio-frequency pulses to alter, and then record, the
behaviour of hydrogen nuclei in tissue water, which produces detailed images of grey matter,
Page 2 of 18
, UNISA | PYC4813 Portfolio Assessment 3
white matter and cerebrospinal fluid (Gazzaniga et al., 2019). PET requires an injected, short-
lived radioactive tracer, most often fluorodeoxyglucose labelled with fluorine-18, and detects
the paired gamma photons produced when positrons from the tracer meet electrons. It there-
fore maps regional glucose metabolism or receptor binding (Raichle & Mintun, 2006).
Table 1: Comparison of MRI and PET in relation to Thabo’s referral question
Aspect MRI PET
Physical basis Nuclear magnetic resonance of hydro- Detection of gamma photons re-
gen protons in a magnetic field leased by a radioactive tracer
Primary informa- Anatomy: tissue structure, lesions, Physiology: regional glucose
tion volume and white matter integrity metabolism, blood flow or receptor
(functional MRI adds an indirect binding
blood-oxygen signal)
Spatial resolution Roughly a millimetre or finer Several millimetres
Safety No ionising radiation, so scans can be Radiation dose from the tracer, which
repeated limits repeat scanning
Practicalities Widely available, no tracer needed, Needs tracer production and a spe-
but noisy and confining cialised scanner, so costlier and
scarcer
Fit to the referral Directly shows whether a lesion, tu- Can show abnormal metabolism but
question mour or injury is present cannot identify its structural cause
The justification for choosing MRI follows from the referral question. The neuropsychologist
needed to know whether neurological damage was present, which is a structural question, and
MRI answers it with the highest spatial resolution and tissue contrast. MRI also avoids ionising
radiation, which matters for a young adult with no suspected degenerative disease. The same
scan allowed the auditory pathway to be inspected, which supported the later exclusion of a
hearing deficit. PET would be considered where a structural scan is normal but a degenerative
process such as early Alzheimer’s disease is suspected, since metabolic change can precede
visible atrophy. That scenario does not fit a 29-year-old with a lifelong developmental history.
A PET scan would also have added cost and radiation exposure without addressing the struc-
tural question (Kolb & Whishaw, 2021).
1.3 Expected MRI findings if a tumour or brain damage caused the poor language expression
Expressive language depends mainly on the left hemisphere in most right-handed people. Broca’s
area in the posterior left inferior frontal gyrus (Brodmann areas 44 and 45), the adjacent left
precentral gyrus and anterior insula support speech planning and production. The arcuate fas-
ciculus connects them with the posterior superior temporal region associated with Wernicke’s
area (Hickok & Poeppel, 2007). A lesion that produced Thabo’s poor expression would most
probably sit in this left frontal and perisylvian network or in its connecting white matter.
Page 3 of 18
