NEUROANATOMY OF DENTAL ANXIETY & FEAR

cererbral gray matter

cerebral cortex

subcortical structures

cerebral cortex

superficial layer

1. mostly cell bodies

2. ridges of cortex (gyri) are separated by grooves (sulci)

subcortical structures are

deep to cortex

cerebral white matter

axons projecting to or from the cortex

prefrontal cortex

frontal lobe located anterior to the cortical motor areas

1. connections with parietal, temporal, and occipital lobes

2. connections with limbic cortex, amygdala, hippocampal formation, thalamic nuclei

regions of prefrontal cortex (PFC)

lateral

medial

orbitofrontal

lateral PFC region

dorsolateral and ventrolateral portions

medial PFC region

dorsomedial and ventromedial portions

orbitofrontal cortex (OFC)

medial and lateral portions

reward / punishment processing, emotional regulation, impulse control

region, size, and activity are linked to anxiety susceptibility

DLPFC

higher order intellectual traits and behaviors / executive functions

1. analytical ability, problem solving, mathematical ability, abstractions

2. goal directed behaviors, delaying gratification, planning

3. rejection of inappropriate alternatives based on past experience (judgement, foresight, decision making)

4. regulatory role for pts to decided to engage in dental care despite negative emotions

conscious awareness of emotions

1. activated in cognitive behavioral therapy for anxiety

VMPFC

site of safety learning / fear extinction

closely linked to emotional behavior and basic drive states (bottom - to - top flow)

1. emotional integration for value-based decision making, personality, appropriate social conduct & responses, motivation, and drive

PFC training or therapy to reduce fear response

increases activity in DLPFC & VMPFC

reduces activity in amygdala

medial orbitofrontal cortex

preferentially activates with positive effect

1. deficient in anxiety disorders

lateral orbitofrontal cortex

preferentially activates with negative effect

1. excess in anxiety disorders

cortical limbic system structures

limbic cortex

1. anterior cingulate gyrus

2. orbitofrontal cortex

3. insular cortex / insula

hippocampal formation

subcortical limbic system structures

amygdala

nucleus accumbens

some thalamic nuclei

hypothalamic nuclei

basal ganglia

anterior cingulate gyrus

modulates sensory perceptions related to emotional, motivational, and attentional changes

1. self control

2. error & conflict monitoring

3. decision-making

4. emotional regulation (including pain response)

5. social cognition

links the limbic cortex with the PFC

reduced connectivity &/or activity with anxiety disorders

insular cortex / insula

multiple, complex functions

1. anterior portion considered part of limbic system

conscious experience of the body’s internal state

1. interoception

integrates information for decision making with connections to anterior cingulate cortex & DLPFC

1. sensory inputs

2. emotions

3. interoceptive stimuli

insula / insular cortex often co-activated with the

amygdala during emotional processing

increased activity with anxiety in all subjects

1. healthy controls and those with a phobia diagnosis

hippocampal formation

medial temporal lobe

memory

1. a “modality” experience from the cortex

   1. sensory, motor, or “higher-order experience”

      1. sent to hippocampal formation for processing by the memory circuit which includes cingulate gyrus

      2. sent back to modality-specific cortex for storage

amygdala

groups of cells also located in medial temporal lobe

1. anterior to hippocampal formation

helps associate stimuli with emotional states

1. emotional state = emotion + associated physiologic (autonomic, endocrine, & skeletomotor) responses

particularly important in how we experience fear

positive emotional responses

associated with amygdala output to the nucleus accumbens

1. considered to be the hub for reward, motivation, & pleasure circuits

negative / stressful emotional responses (such as fear)

associated with amygdala output to multiple areas

specific type of brain activity (epileptiform discharges) from the amygdala produce feelings of fear or dread

amygdala attaches

emotional significance to stimuli

amygdala plays a key role

processing threats

1. anterior cingulate cortex & insula process the potential threat

learned helplessness

1. behavior exhibited after enduring repeated aversive stimuli beyond their control

2. related to self-efficacy (belief that you can achieve your goals)

   1. amygdala mediates fear and anxiety responses to uncontrollable stressors

limbic system basal ganglia

collection of subcortical nuclei

modulate movement

some of the nuclei are also associated with emotional regulation

1. healthy control groups demonstrate more connectivity with these areas than those with dental phobia