FRONTAL LOBE
Location
The frontal lobes include all tissue anterior to the central sulcus, which separates the frontal
lobe from the parietal lobe.
It is superior to the lateral sulcus, which separates the frontal lobe from the temporal lobe, and
is the most anterior part of the brain.
This vast area constitutes 30 -35 % of the neocortex
Anatomy
It has two lobes which are divided by the longitudinal fissure.
The frontal lobes are subdivided into the:
• Primary Motor Cortex (M1), which is on the precentral gyrus,
• Premotor cortex which is anterior to the motor cortex and comprises Broca’s area. It
also includes the dorsal region is called the supplementary motor cortex and, below it
is the dorsal and ventral premotor cortex and the inferior frontal gyrus.
• The prefrontal cortex makes up the area anterior to motor, premotor and cingulate
cortex (limbic system). The prefrontal cortex can be divided in to:
o the dorsolateral prefrontal cortex: has reciprocal connections with the posterior
parietal areas & superior temporal sulcus
o the orbitofrontal cortex: communicates with the temporal lobe, amygdala &
hypothalamus (for hearing, vision, emotion, sensation, taste & smell)
o the ventromedial prefrontal cortex.
• Anterior Cingulate Cortex has recently been thought of, in light of economo neurons,
as specialised neocortex making extensive connections with the motor, premotor and
prefrontal cortex.
Function
The general function of the frontal lobe is the temporal organisation of behaviour. Thus, the
frontal lobe contains control systems that implement different behavioural strategies in
response to both internal & external cues
The left frontal lobe has preferential role in language-related movements like speech and has
a greater part in encoding information into memory, while the right frontal lobe plays a greater
role in nonverbal movements like facial expressions and is more engaged in memory retrieval.
Both lobes play a role in all behaviours. Anterior cingulate cortex makes extensive bidirectional
connections with motor, premotor, prefrontal and insula.
The premotor and prefrontal regions contribute in different ways to this control function.
The motor cortex is responsible for making movements.
The premotor cortex selects movements.
The prefrontal cortex controls cognitive processes so that appropriate movements are
selected at the correct time and place
Primary Motor cortex controls movement force and direction and specifies elementary
movements like in mouth and limbs.
Cells project to basal ganglia (associated with learning, movement and smoothly executed
responses), red nucleus (cranial nerves and motor functioning) and spinal cord (reflexive
motor functions).
, Premotor Cortex is active in choosing movements from movement lexicon and contains mirror
neurons that recognise other’s movements and select similar or different actions, as well as
selecting and directing motor sequences.
It functions primarily to select behaviours in response to external cues and can make a greater
internal contribution when no such targets are available.
Not only are motor acts paced by cues, but they also can become associated with cues
Prefrontal Cortex is involved in emotional behaviours and controls cognitive processes that
select appropriate movements.
This selection may be controlled by internalized information or by external cues or it may be
made in response to context or self-knowledge
Internal Cues:
The internalized record of what has just taken place is independent of existing sensory
information and can be called temporal memory, working memory, or short-term memory
• Temporal memory → neural record of recent events and their order
These events may be related to things or to movements and thus derive their information
from the object-recognition or motor streams of sensory processing
The dorsolateral areas are especially engaged in the selection of behaviour based on
temporal memory
External Cues:
People whose temporal memory is defective become dependent on environmental cues to
determine their behaviour
That is, behaviour is not under the control of internalized knowledge but is controlled directly
by external cues
People with frontal-lobe injuries have difficulty inhibiting behaviour directed to external stimuli
One type of environmental cue is feedback about the rewarding properties of stimuli
Context Cues:
Our behaviour is role (e.g. parent vs. lover) & context (e.g. library vs. picnic) dependent
Hence behaviour that is appropriate at 1 moment may not be appropriate if there are subtle
changes in the context
The choice of behaviours in context requires detailed sensory info which is conveyed to the
inferior frontal cortex from the temporal lobe
Context also means affective context, and this contribution comes from the amygdala
People with orbitofrontal lesions have difficulty with context, especially in social situations
Autonoetic Awareness:
• Def → autobiographic knowledge
Our behaviour is also affected by a lifetime of experiences and goals
Autonoetic awareness allows one to bind together the awareness of oneself as a continuous
entity through time
Impairment in autonoetic awareness results in a deficit in the self-regulation of behaviour
Patients with orbital frontal damage often lose this self-knowledge & have real difficulty in
daily living
Prefrontal regions receive significant input to regulate how prefrontal neurons react to stressful
stimuli which contributes to emotional states.
Effects of brain damage
Tasks that challenge frontal lobe patients:
i) Planning in advance & selecting from many options
ii) Ignoring extraneous stimuli & persisting in the task at hand
