external image SUPRAMARGINALGYRUSarea57.jpgNeurons in area 5, as well as those located in the insula, receive direct thalamic input from the ventral and posterior portion of ventral parietal lobe (VPL). The ventral portion in particular in addition to somesthetic information, may also convey pain sensation to the parietal lobe.
Some neurons located in area 5 and 7 of the parietal lobe also demonstrate pain sensitivity, with some are 7 neurons responding exclusively to thermal and nociceptive stimuli with area 5 presumably acting to localize the source of pain.

Electrical stimulation: to parietal lobe resulted in the sensation of pain, albeit about 1% of the time

Damage/Injury (either hemisphere but particularly right side): when the more inferior portion of area 5, 7 or the supramarginal gyrus (Broadmann's area 40) has been destroyed, patients may demonstrate:
-Lack of emotional responsiveness to painful stimuli
-Indifference
-Increased pain threshold
-Tolerate pain for an unusually lengthy time period and fail to respond even to painful threat

Brain Regions and Pain:
Subcortical lesions (esp. thalamus, less often with destruction of ant. cingulate):
-Loss of sensation or an inability to react to pain
At the neocortical level, although pain responsiveness may be diminished or absent following damage to these tissues, elementary sensation remains intact and the ability to differentiate, for example, between dull and sharp is retained. The deficit is usually bilateral.

Somatosensory Areas 1 &2: Pain, touch, temperature sense, pressure sense, position sense, vibration sense, sensation of movement
Prefrontal area: Pain, executive function, creativity, planning, empathy, action, emotional balance, intuition
Anterior Cinguate: Pain, emotional self-control, sympathetic control, conflict detection, problem solving
Posterior Parietal Lobe: Pain, sensory, visual, auditory perception, mirror neurons, internal location of stimuli, location of external space
Supplementary Motor Zone: Pain, planned movement, mirror neurons
Amygdala: Pain, emotion, emotional memory, emotional response, pleasure, sight, smell, emotional extremes
Insula: Pain, quiets the amygdala, temperature, itch, empathy, emotional self-awareness, sensual touch, connects emotion with bodily sensation, mirror neurons, disgust
Posterior Cingulate: Pain, visuospatial cognition, autobiographical memory retrieval
Hippocampus: Helps to store pain memories
__//Orbital Frontal Cortex://__ Pain, evaluates whether something is pleasant vs. unpleasant, empathy, understanding, emotional attunement(1)

Body Image and Pain
Schilder, has argued that the loss of reaction to pain is due to disturbances in the image of the body. That is, the experience or threat of pain is no longer related to the body image. Geschwind however, raises the possibility that this condition is due to disconnection from the limbic system. If this were the case, somesthetic (painful) sensation would no longer be assigned emotional significance and would thus implicate the insular region of the parietal lobe, which also receives visceral as well as somesthetic information and funnels this data to the limbic system.

This same insular-limbic pathway may serve to promote tactile memory; that is, via the funneling of complex somesthetic information to the hippocampus and amygdala. Conversely, it may be this same pathway which when abnormally activated or injured, may give rise to abnormal emotional significance being attributed to bodily sensations.

-G. Moseleey studies on body image and pain sensations
-Catherine Preston study on illusions of digitally stretching out hands on a screen decreased perceived osteoarthritic pain (1)

PAIN AND HYSTERIA

Destruction of the inferior portions of areas 7, 5, and 40 may result in loss of pain sensation however When the injury is secondary to tumor or seizure activity patients may instead report experiencing pain as well as sensory distortions that concern various body parts due to abnormal activation of the parietal neocortex.
Important to note: although the predominant focus for paroxysmal pain is the right hemisphere, pain also has been reported to occur with tumors or seizures activity that involves the left parietal region.

Unfortunately, when the patient's symptoms are not considered from a neurological perspective, their complaints with regard to pain may be viewed as psychogenic in origin. This is because the sensation of pain, stiffness, engorgement, is, indeed, entirely "in their head" and based on distorted neurological perceptual functioning. Physical exam may reveal nothing wrong with the seemingly affected limb or organ. Thus such patients may be viewed as hysterical or hypochondriacle, particularly in that right hemisphere damage also disrupts emotional functioning.


(1) - Doidge, Norman. The Brains Way of Helaing: Remarkable Discoveries and Recoveries from the Frontiers of Neuroplasticity