Frontal lobe - Anatomy, Functional areas briefly and Function tests in length with Psychiatric approach

1. By
Dr.Balaji Sainath.A
1st year PG

2. Introduction
 Compared with brains of other primate speices, the human
brain is substantially greater in size with certain areas
expanded disproportionately,
 The prefrontal cortex occupies 3.5% of total cortical volume
in cats, 11.5% in monkeys, where as in humans it occupies
30%.
 Conversely, the relative representation of other areas
decreased, eg:- primary visual cortex occupies only 1.5%
area in humans, where as 17% in monkeys.
 In addition, substantial differences in the organization of
certain elements of neural circuitry like dopaminergic
innervation make human brain distinctive than other
speices.

3. Development

4. Contd..
 From the developmental point of view, the cerebral cortex
consists of,
1) The hippocampal cortex (in medial wall)
2) The pyriform cortex (in marginal layer superficial to the corpus
striatum)
3) The neocortex (in superolateral region)
 The hippocampal cortex is subdivided into superior, middle,
lower parts,
1) Superior part separated by corpus collosum and formed as
indusium griseum
2) Middle part forms a ring like configuration along curve of
choroid plexus
3) Lower part forms hippocampus, dentate gyrus

5. Contd..
 The pyriform cortex forms the cerebral cortex that recieves
olfactory sensations, uncus, anterior part of
parahippocampus gyrus, anterior perforated substance.
 The neocortex is the largest part that is expanded by
migration of cells from mantle layer into the overlying
marginal layer, which forms several cell layers &
considerable side to side expansion leads to ↑↑↑surface
area.
 As the surface expansion is at greater rate than that of the
hemisphere as a whole, the cortex becomes folded on
itself..

6. Frontal Lobe
 Frontal lobe is the largest lobe, it is 1/3 of each
hemisphere
 Extends from central sulcus to the frontal pole
 Lies above the lateral sulcus and anterior to the
central sulcus
 The frontal lobe contains most of the dopamine
sensitive neurons in the cerebral cortex. Dopamine
associated with reward, attention, long-term working
memory, planning and drive.

7. Anatomy

9. Contd..
 On medial surface of FL:
1. corpus callosum
2. cingulate gyrus
3. paracentral lobule
4. medial central gyrus
 On inferior surface of FL:
1. olfactory bulb and tract

11. Functional areas

12. Contd..
 4 (MS1) Contralateral hemiplegia
 MS2 Bilateral flexor hypotonia without paresis &
paralysis
 Paracentral lobule Bowel & bladder control
 6 Loss of skilled movements (extrapyramidal system)
 6,8 Loss of conjugate eye movements
 44,45 Broca’s aphasia
 9,10,11,46,47 *(silent area of brain)

13. Prefrontal cortex
 It can be divided into dorsolateral, ventrolateral,
orbitofrontal, medial prefrontal and frontopolar areas.
 Dorsolateral area have broadman areas 8,9,10,46,47 &
Orbitofrontal area have areas 11,47.
 The dorsolateral prefrontal region is important for
cognition, executive function, and focussed attention.
 The orbital prefrontal region is important for social
conduit, insight, judgement, and mood.

22. Functional anatomy of Frontal lobe
 There are two type of circuits
1.Cortico-cortical
2.Cortico-subcortical
 There are five Cortico-subcortical circuits
A. Motor circuit (motor, premotor)
B. Oculomotor circuit (frontal eye field)
C. DLPFC (executive function)
D. ACC (motivation)
1. DACC-attention
2. SGACC-emotions
E. Orbitofrontal circuit- impulsivity

23. Corticocortical
 Several important
prefrontal corticocortical
circuits are shown in this
diagram. The ACC has
corticocortical interactions
with DLPFC and OFC. The
OFC in turn, has
corticocortical with
hippocampus. The DLPFC
has only sparse
connections with amygdala
and hippocampus.

24. Cortico-subcortical
 The prefrontal cortex
projects to striatal
complex, which projects to
thalamus, which feeds
back to PFC. The CSTC
loop can be modulated by
neurotransmitter nodes
that project to cortex
thalamus or striatum. In
figure B serotonin projects
to all three regions and
inhibits out put.

25. CSTC loop for executive function
o CSTC loop involves
DLPFC and the rostral
top part of the caduate
with in the striatal
complex.

26.  Loop arising from ACC
and projecting to the
bottom of striatum, then
thalamus and back to
ACC.

27.  CSTC loop originating
in the ventral, or
subgenual, ACC and
projecting to the nucleus
accumbens, then the
thalamus and back to
subgenual ACC.

28.  Motor activity such as
hyperactivity and
psychomotor agitation or
retardation can be
modulated by cortico-
thalamic-cortical loop
from the prefrontal
motor cortex to the
putamen to thalamus
and back to the PFC.
PFMC – putamen- thalamus- cortex

29. Frontal lobar function tests
Dorsolateral prefrontal cortex
1) Insight (R>L)
2) Judgement (L>R)
3) Attention (R>L)
Observation during examination
Digit repetition - Forward(7+/-2), Backward(5+/-2)
Serial 7 substraction
Months in reverse order
Spell backwards
Go No-go test
*Sustained attention – ‘A’ random letter test
(omission/commission/perseveration)

30. Contd..
4) Abstract thinking (L>R)
Proverb interpretation
Similarities
5) Cognitive estimation test (general IQ)
6) Verbal fluency
Total animals
Total vegetables
FAS test
7) Sequencing tests
Luria’s test of alternate sequencing (visual pattern)
Luria’s alternating motor patterns test

32. Contd..
8) Formal testing
Wisconsin cord sorting test
Trail making test
Stroop Color & Word test
Tower of London test

37. Contd..
Orbital & Basal area
1. Go No-go test
2. Stroop Colour & Word test
Primary motor area
1. Motor strength of hand grip
2. Motor speed as in finger tapping
Premotor area
Sensorimotor abilities are tested by asking the patient to
touch each finger to the thumb in succession as rapidly as
possible. Watch for speed and dexterity.

38. Contd..
Frontal eye fields
Tested by asking the patient to rapidly refixate eyes b/w two
targets.
Brocas area
Speech and Language testing
 lack of spontaneity in speech, Telegraphic speech,
Perseveration of speech, Tendency to whisper and
Dysarthia.
 verbal fluency(↓), comprehension(+ except grammar),
repetition(-), naming(-) and word finding, reading,
writing, spelling

39. Bedside tests for frontal lobe
 Luria’s 3 step test
 Alternating hand movements test
 Verbal fluency FAS test
 Cognitive estimation task
 Abstract thinking
 Go No-go test (perseveration)
 Written alternate sequence task
 Grasp reflex
 Palmo-mental reflex
 Glabellar tap

40. Frontal lobe (executive) syndrome
 Certain clinical features emerge with especial
frequency after damage to frontal lobes.
 In the typical case, the personality of the patient is
more profoundly and obviously affected than his
cognitive functions.
 Lack of initiative and spontaneity is usually coupled
with a general diminution of motor activity.
 In consequence the capacity to function independently
in daily life can be profoundly affected.

42. Classical case reports
 Harlow (1868 [1993]) described the case of Phineas
Gage, a railway engineer in New England.
 Eslinger and Damasio (1985) described a somewhat
similar patient. This man was chief accountant, a
college graduate.
 Shimamura (2002) has described similar phenomena
in the photographer Eadweard Muybridge.
 A more specific deficit was described by Lhermitte
(1986), who reported imitation and so-called
‘utilisation behaviour’ in patients with frontal lobe
lesions.

44. Diseases commonly associated with
Frontal lobe

45. Contd..

46. Contd..
Frontal lobe epilepsy
 2nd most frequent focal form
 Age of onset 9yrs @LT sided, 11yrs @RT sided
 Typically brief (<30sec), usually sleep related
 c/o often awakens from sleep with opened eyes, frightened
expression, consciousness briefly disturbed and rapidly
recovers
 Larger attacks (2-3min) associated with epileptic nocturnal
wanderings, frightened child might scream and attempt to
escape and violent drop attacks in an awake child
 Tonic seizures originate @ supplementary motor area
 CPS originate @orbital, medial, polar, dorsolateral areas

47. Contd..
 EEG – normal, not diagnostic
 Often associated with reduced attention span,
psychomotor speed
 Frequently misdiagnosed as parasomnias
 Responded well with anticonvulsants