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Frontal Lobes especially PFC (Heteromodal) (Assessment of Frontal Lobe…
Frontal Lobes especially PFC (Heteromodal)
Subdivisions
Premotor Cortex (Areas 6,8,44)
PMd: choosing movements from a movement lexicon
PMv: mirror neurons
FEFs (area 8): receive visual input from posterior parietal, superior colliculus --> control eye movements
all receive projections from dlPFC, PMd & Pmv receive also from parietal regions
Functions: selecting behaviors in response to external cues (supplementary motor: internal contribution when no cues)
Prefrontal Cortex
OFC
input from all sensory modalities
projects to amygdala & hypothalamus (controlling blood pressure, respiration etc.)
physiological changes important in emotional responses
reversal learning, encoding visual information, encoding unpleasant auditory information
Orbitomedial: emotional & instinctive behavior due to limbic connectivity, inhibitory control of interference
OCD: Hyperfunction of omPFC/OFC --> abnormal hyper function of inhibitory control
role in reward expectations, anticipation & processing of outcomes
VmPFC
cortical connections from dlPFC, posterior cingulate, medial temporal
connects sub cortically with amygdala, hypothalamus & PAG in brainstem
linked with structures capable of emotional behavior bodywide
evaluation of faces, autobiographic memory
role in decision making & retrieval of information from long term memory
bimanual coordination, attention to demanding tasks, modulation of body arousal, spatial memory, conflict resolution
DlPFC
understanding of its functions lies in relation to posterior parietal cortex, also connections with cingulate cortex, basal ganglia, superior colliculus
self-ordering, conditioned learning, verbal & nonverbal working memory, visuomotor skill learning
rirght: anosognosia --> lack of self-awareness
temporal organization/integration of behavior: can continuously reconcile the past with the future & keep the action in logic order and on target
all domains of voluntary action e.g.. speech, logical reasoning
Schizophrenia: failure in proper temporal integration of the thought process (internal action), blocking, looseness of associations
receives projections from dm nucleus of thalamus
input from mesolimbic dopamine cells in tegmentum --> regulating reactions to stimuli
selecting appropriate movements at correct time & place (selection may be controlled by internal or external, or context cues)
Autonoetic awareness: lifetime of experiences & goals --> self-knowledge, self-awareness (medial & ventral frontal injury leads to impairment)
Primary Motor Cprtex (Area 4)
elementary movements, control of movement force & direction
projection to subcortical motor structures: Basal Ganglia, Red Nucleus, Spinal Cord
making movements
Anterior Cingulate Cortex
Networks
Default
mind wandering: active when resting rather than when engaging in cognitive tasks
thinking about one's past & future
Salience
ACC, Supplementary Motor, Anterior Insula
active when behavioral change is needed, modulates other networks' activities
if not functioning properly --> default network excessively active
Assymmetry (relative)
different roles in memory processing
left: encoding information
right: memory retrieval
both frontal lobes play a role in nearly all behavior
Cognitive control?
no clear boundary to EF
Priotization, Selection, Inhibition, Reducing Uncertainty, making choices
Symptoms of Frontal Lobe Lesions
Impaired social behavior (orbital, dl PFC)
Altered sexual behavior (Orbital)
Poor temporal memory (dlPFC): poor WM & delayed response
Impaired olfactory discrimination (Orbital)
Environmental control of behavior (Prefrontal & Orbital): Poor response inhibition, impaired associative learning, risk taking, rule breaking, gambling, self-regulatory disorder
Personality changes (Orbital): pseudodepression & pseudopsychopathy
Loss of divergent thinking (orbital & dlPFC): reduced spontaneity, poor strategy formation, poor frequency estimate
Disturbance of Motor Function (mostly motor ares 4,6 & language Broca's area 44): loss of fine movements, loss of strength, poor movement programming, poor voluntary eye gaze, Broca'a Aphasia
Assessment of Frontal Lobe Damage
EF --> Frontal Assessment Battery, BADS
Response Inhibition --> Stroop, Wisconsin Card Sorting
Verbal Fluency --> Thurstone Word Fluency
NonVerbal Fluency --> Design Fluency
Planning --> Tower of London
Working Memory --> self-ordering, Wechsler Memory Scale, digit span, CVLT
Motor function --> tests of strength, finger tapping speed
Attention
--> operational (high speed, highly structured) e.g.. Stroop
--> tactical (focused or divided attention)
--> strategic (unstructured) eg. Wisconsin Card Sorting
Language --> aphasia screening tests
Intelligence? General g factor
frontal lobe injuries have little effects on standard IQ (crystallized intelligence)
Prefrontal-Parietal Network
fluid intelligence affected: problem solving tasks (activity in dlPFC & mPFC & posterior parietal)
Disorders Affecting Frontal Lobe
schizophrenia
Parkinson
chronic stress
Korsakoff's
Drug Addiction
Somatic Marker Hypothesis
OFC doesn't have factual information but provides somatic markers so that we can learn by experience
vmPFC responsible for linkage between factual sets & emotional sets
people who fail to develop context appropriate somatic markers --> stimulus-bound behavior typical of sociopathy