07a association cortex frontal lobe

Director Function

Stretch Reflex

Withdrawal and Crossed Extensor Reflex

Locomotion

Autonomic Regulation of Cardiovascular Function

Emotional Circuit

Evolution of Brain

Anatomical organization of Cerebrum

Grey Matters

The Association Cortices

Cortical Architecture

Intracortical circuits

Cortical Lamination

Brodmann's cytoarchitectonic mapping of the human brain

Broadman's # NAME FUNCTION 17 Occipital Lobe Visual Projection Cortex 18 Visual Association Cortex 19 Posterior Parietal Lobe Visual Association Cortex 37 Tempero-parietal-occipital area General Sensory Association Cortex 39 Angular Gyrus Word Recognition 40 Supramarginal Lobe Somatosensory Association Cortex 1,2,3 Postcentral Gyrus Somatosensory Projection Cortex 5, 7 Superior Parietal Lobule General Sensory Association Cortex Middle 1/3 of Superior Temporal 41, 42 Auditory Projection Cortex Cortex 22 Superior Temporal Gyrus Auditory Association Cortex 21, 20, 38 Inferior Temporal Cortex General Sensory Association Cortex 4 Precentral Gyrus Primary Motor Cortex 1,2,3 Postcentral Gyrus Somatosensory Projection Cortex 6,8,9 Premotor Cortex Motor Association Cortex Middle 1/3 of Superior Temporal 41, 42 Auditory Projection Cortex Cortex Motor Association Cortex - Specific to 44,45,46 Broca's Area speech 10 Preftontal Cortex General Motor Association Cortex 11 Orbital Gyri General Motor Association Cortex

Input-output relationships of cortex.

Cerebral Cortex and Thalamus

Noradrenergic neurons in the pons Important for focused attention

Dopaminergic neurons in the brain stem and hypothalamus Dopamine in the caudate nucleus facilitates posture, whereas dopamine in the nucleus accumbens is associated with an animal's speed (and pleasure).

Serotonergic Cell Groups Serotonin seems to have distinctive actions contributing to anxiety and impulsive behavior. Patients with evidence of low serotonin levels have attempted suicide by very dramatic means, such as cutting the throat

Cholinergic Cell Groups (wake sleep cycle)

Sensory Pathway

Visual Pathway

Auditory Pathway

Taste Pathway

Corticospinal tract

Cerebral Cortex: Functional Organization

Association cortices

Pathways to the somatosensory, visual, and auditory association areas

Unimodal sensory inputs converge on multimodal association areas

The Sequence of Information Processing Is Reversed in the Motor System

Sensory Motor Association Cortex

Frontal Lobe is an “Essence of Human being” Gives our capacity to feel empathy, sympathy, understand humor and when others are being ironic, sarcastic or even deceptive.

Evolution of Human Frontal Lobe The high, straight forehead that characterizes modern humans, superceding the prominent brow ridges of our ancestors, is due to the expansion of the cortex, and especially the prefrontal cortex, in our species. 1. Australopithecus robustus 2. Homo habilis 3. Homo erectus 4. Homo sapiens neanderthalensis 5. Homo sapiens sapiens

Phinease Gage (1848) 1. He becomes unreliable and fails to come to work and when present On 13th Sept 1848 a railroad he is "lazy." 2. He has no interest in going to worker hard working, church, constantly drinks alcohol, diligent, reliable, responsible, gambles, and "whores about." 3. He is accused of sexually molesting intelligent, good humored, young children. polite god fearing, family 4. He ignores his wife and children and fails to meet his financial and oriented foreman family obligations. 5. He has lost his sense of humour. Following an explosion iron bar 6. He curses constantly and does so drove into frontal lobe in inappropriate circumstances. 7. Died of status epilepticus in 1861

Frontal Lobe ablation in Monkey and Dogs (Bianchi) "The frontal lobes are the seat of coordination and fusion of the incoming and outgoing products of the several sensory and motor areas of the cortex" (Bianchi, 1895) • Loss of "perceptive power", leading to defective attention and object recognition. • Reduction in memory. • Reduction in "associative power", leading to lack of coordination of the individual steps leading towards a given goal, and thus to severe difficulty solving anything but the most simple problem. • Altered emotional attachments, leading to serious changes in "sociality" [one of the main aspects of Phineas Gage's post-traumatic behaviour]. • Disruption of focal consciousness and purposive behaviour, leading to apathy and/or distractibility [one of the main aspects of Becky's post- operative behaviour]. Bianchi 1922

History Dandy’s (1936) Jacobson (1935) – following bilateral frontal – Premotor lobotomy in lobotomy during removal of primates -> meningioma – Social indifference Feuchtwanger (1923) – Tameness 200 case of frontal lobe injury – Lack of initiative – Placidity – Vacillation – Forgetfulness – Euphoria – Difficulty in problem solving – Inattentiveness – Normal intellect and memory Egas Moniz 1935 – Prefrontal lobotomies in psychotics

Inferiomesial Frontal leukotomy Egas Moniz 1935 Hours Weeks to months – Drowsy – Apathetic – Regained memory and – Incontinent intellect – Akinetic – With personality changes – Mute – Indifferent to the others Days problem – Decreased initiative – No thought to their conduct – Lack of concern – Freedom from anxiety – Tactless – Apathetic – Distractible – Socially inept – Euphoria and emotional outburst

Frontal lobe and Psychiatry Schizophrenia : – Involving dorsolateral Personality disorder: Antisocial prefrontal cortex Personality disorder with impulsivity of – affective changes, impaired motivation, poor insight. and frontal lobe other "defect symptoms Attention deficit syndrome with – Evidence : Neuropathologic distractibility of frontal lobe studies, (23) in EEG studies, (24) in radiological studies using CT measures, (25) with MRI, (26) and in cerebral blood flow (CBF) studies.

Attention skills Selective attention: the ability to efficiently 'filter' information; to detect information that is relevant and ignore irrelevant or distracting information. Sustained attention: the ability to actively attend to a task, goal, or own behavior despite there being little stimulation for such continued processing. Divided attention: the ability to monitor or attend to two things at once. Shifting attention: the ability to shift attention between two or more tasks.

Thinking skills Organization: the ability to arrange or place things in a meaningful system. Planning: the ability to create a 'blueprint' or strategy for reaching goals or completing a task. Time management: the ability to effectively estimate how much time one has, how to spend that time, and how to stay within time limits and meet deadlines. Working memory: the ability to hold information in immediate awareness while performing a mental operation on that information. Metacognition: the ability to think about one's own thoughts, behaviors, and feelings in a given situation. It involves being able to self-monitor or evaluate one's skills.

Monitoring skills Response inhibition: the ability to think before acting. Doing so, gives one the time to evaluate a situation and determine how one's behavior might affect it. Self-regulation of affect: the ability to manage emotions in order to achieve goals, complete tasks, or control and direct behavior. Task initiation: the ability to start a task without procrastinating. Flexibility: the ability to revise plans or directed behavior when there are obstacles, setbacks, new information, or mistakes; adapting to environmental changes. Goal-directed persistence: the ability to self-motivate and see things through to completion or reaching of a goal.

Prefrontal cortex ~ 1/3 of cortical surface Most recently evolved Well developed only in primates – the advent of the human species: "age of the frontal lobe" develops late in ontogeny – differentiation through age 1 – maturation through age 6

Connectivity of Prefrontal regions Input from association cortex (occipital, parietal, temporal & olfactory areas) convergence of higher-order input from all modalities. Reciprocal connections: prefrontal processing modulates perceptual processing. LIMBIC connections (memory/emotion) Input to premotor areas - controls/programs behavior.

Premotor & Motor Areas Premotor areas (6) - input from prefrontal regions and parietal association areas (5,7). Area 4: primary motor cortex – input from premotor area (6) and area 44 – sends output to spinal cord, and other motor structures (basal ganglia) Frontal network controls voluntary, planned actions.

“Planning Neurons” in the Monkey Frontal Cortex

Neuron Firing in the Principal Sulcus track the working Memory

Working Memory

Imaging of Working Memory

Interaction Among Association Areas

Beyond Motor Planning Frontal lobe has evolved from being the main motor planner/organizer to a higher level behavioral/strategic planner/organizer. Mental model, considering options, selecting behaviors based on context, feedback, stored knowledge Making predictions about what will work.

Impaired divergent thinking Decreased consideration of alternative strategies/ behaviors; reduced flexibility Decreased spontaneity, initiative, may appear lazy, unmotivated Knowledge/intelligence may seem intact (e.g. IQ) but its not used to generate strategies or solve problems efficiently

Decreased Inhibition Problems inhibiting incorrect/ineffective responses & switching to a new strategy Perseverates; not responsive to feedback or changes in environment Violates rules, expectancies; takes risks Not adaptable Decreased social inhibitons as well

Impaired association learning Reduced response to consequences Impaired on delayed response tasks Impaired responsiveness to social & contextual cues

Impaired temporal learning Impaired memory for order Could affect problem-solving, planning and impair systematic, organized behaviours

Personality and emotional changes Apathetic, indifferent, loss of initiative, lack of emotion or somewhat depressed, little verbal output. Most common after left frontal damage; called "pseudodepression" Lack of tact & restraint, immature, coarse,lack of social graces, inappropriate sexual behavior, increased motor activity. More common after right frontal damage; called "pseudopsychopathic"

Memory defect Part of more general disturbance in thinking Can recall the details of problem, error in trying to solve Could not put them to use in the correction of further performance. Cannot categorizes series of item in group for recall

Frontal lobe and arousal Right frontal lobe exerts bilateral influences on arousal The right frontal lobe is also larger than the left suggesting a greater degree of interconnections with other brain tissue, and it appears to exert bilateral inhibitory influences on attention and arousal However, because the right frontal lobe appears to exert bilateral inhibitory influences, whereas the influences of the left are unilateral and excitatory, when the left frontal region is damaged, the right may act unopposed and there may be excessive left cerebral inhibition or reduced activity

Personality and behavior Lack of initiative and spontaneity Placidity: worry, anxiety, self concern, hypochondriasis, and pain reduces Psychomotor retardation: number of movements, spoken words and thought per unit of time diminish. Mild form abulia and severe akinetic mutism. Organic driveness: brief but intense meaningless activity. Loss of ego strength: Witzelsucht or moria : socially uninhibited and lack aunawerness of their abnormal behavior. Loss of regards to social conventions , only interested in personal gratification.

Disinhibited sexuality It is not unusual for a hypersexual, disinhibited frontal lobe injured individual to employ force. Seizure activity arising from the deep frontal regions have also been associated with increased sexual behaviour, including sexual automatisms, exhibitionism, genital manipulation, and masturbation

Summary Frontal lobe function Motor Cognitive Behavior Arousal Voluntary Memory Personality Attention movements Language Problem solving Social and sexual Expression Eye movements Judgment Impulse control Initiation Abstract Mood and affect thinking Spontaneity

07a association cortex frontal lobe

by PS Deb

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