Clinical Neuropsychology L6 FRONTAL LOBES

-Planning and selecting from many options

Executive function

-Ignoring external stimuli irrelevant to your task and persisting inthe task at hand (internal stimuli)

Assessing internal & external stimuli for behavioral control 

-Keeping track of what already happened andwhat is to come

Keeping an internal temporal record

- Executive function (planning, organization and execution of more or lesscomplex action)- Assessing internal and external stimuli in behavioral control- Keeping track of what happened and what is to come, relying on focusedand selective attentionThe frontal lobe therefore has strong control over automatic, spontaneous reactions; impulse control

- controls motor neurons in brainstem and spinal cord- influence on control also from the premotor cortex, which sends motor signals to the brainstem and spinal cord itself

- includes also the supplementary motor area, frontal eye fields and Broca’s area- receives info from the posterior parietal cortex and dorsolateralprefrontal cortex (DLPFC) for planning and guidance of eye and limb movement

Dorsolateral prefrontal cortex:

Orbitofrotal cortex

Ventromedial prefrontal cortex

reciprocal connections with the posterior partietal cortex(visual dorsal stream) and STS (also see Ch 15) as well as motor areas

DLPFC relies on information from posterior cortex areas about

• Executed movements; info from the (parietal) dorsal stream• Objects in the environment; info from the (temporal) ventral streamDLPFC engaged in selecting behavior based on temporal/working memory

receives majority of information from thetemporal lobe;- Auditory area (superior temporal gyrus)- Visual ventral stream (inferior temporal gyrus)- Polymodal area (STS)- Amygdala

• Information from the temporal cortex (STS) and amygdalaregarding social and affective valence of stimuli (external)• Your personal reference (life goals, experiences - internal)

- blunted activity to goal-related tasks in addiction- fronto-orbital lesions: problems adapting behavior to social context(following personal rules and moral norms)

receives major input from the medial temporal area, but also olfactory system

- Reciprocal connections with the amygdala: controllingemotional and social behavior (cognitive evaluation; “isfear justified in this situation?”)

- Projects towards the hypothalamus:(control over autonomic physiological responses like blood pressure, heart rate, breathing  important in emotional reactions), and brainstem (for emotional ‘fight-flight’ responses)

Functions involve inhibition, control of emotional responses and decision making  e.g. phobia versus generalized anxiety disorder

Dorsolateral prefrontal cortex: cognitive“cool executive functions”Working memory, sustained attention, problemsolving non-motorOrbitofrotal cortex and Ventromedialprefrontal cortex: emotion, motivation;“hot executive functions”

Evaluation of stimuli depending on value(positive/negative) and reward

range of sensorimotor, cognitive, and affective processes

Middle zone: cognitive control, pain,affectPosterior zone: motor functionsAnterior zone: default mode network:reward, social processing, episodicmemory

Asymmetry of frontal lobe functions is less pronounced than asymmetry in the temporal or parietal lobe. Also, frontal lobe asymmetry is hard to assess due to its involvement in almost every form of behavior.

Note: asymmetry in the affective functions are way more complex in real life!

The different frontal areas (DLPFC, OFC, anterior cingulate gyrus) are pretty much active simultaneously within the frontal network. 

Dominant for language relatedbehavior, e.g. spontaneous speechTask settingPredisposition for approachingbehavior (“appetitive behavior”)

Somewhat dominant for constructivetasks and facial expressionTask monitoringPredisposition for avoidant behavior

Motor disorders

loss of precision and speed of fine hand and speech movements, and loss of force of limb movements

Problems with performing movement sequences (inclusive speech)

However, fast recovery due to compensation by contralateralhemisphere (due to bilateral premotor influences on motorbehavior)

 Problems with reproducing series of movements in a correct order,especially with facial movements

 Decline in spontaneous facial expressions and other types ofexpressive motor behavior Difficulties with control of gaze direction; problems with visualsearch tasks (probably damage of frontal eye fields) Difficulties with speech and/or generating words or sentences(lesion Broca's area / supplementary motor area)

 Lack of spontaneous languageproduction ("word fluency", "verbalfluency"; particularly with L-sidedlesions) and other spontaneousexpressions of cognitive activity (a.o."design fluency"; especially with R-sided lesions) Lack of initiative and concentration inacting and thinking; lack of creativity Concentration problems; being quicklydiverted Lack of new strategies to resolveproblems

 Perseveration in responding, acting,and thinking with changingenvironmental conditions (e.g.,Wisconsin Card-Sorting Test) Loss of response inhibition (e.g.,Stroop Test), signs of disinhibition Not following rules, taking more risk

 Disturbances of episodic memory (memory of personal events andexperiences; see Ch. 18) Problems with associative learning (selecting of appropriateresponse to a certain stimulus)

 identity objects (what, which?) location objects and events (where?) temporal order of events (earlier, later?)with L-sided dominance for verbal material and R-sided dominance for non-verbal material

- difficulty understanding the meaning of facial expressions- unpredictable, defiant, moody behavior- pseudo-psychopathy: primitive behavior, lack of tact andmanners, (sexual) disinhibition (relation with right-sidedlesions; lack of avoidant behavior)- pseudo-depressive behavior: apathy; lack of initiative,indifference (relation with left-sided lesions; lack ofapproaching behavior)

• Degenerative brain disease: atrophy frontal and temporal lobes• Onset most often between 40-60 years• Different symptoms: behavior, language, motoric