Chaipat Chunharas

A newly identified locus for benign adult familial myoclonic epilepsy on chromosome 3q26.32-3q28

Benign Adult Familial Myoclonic Epilepsy (BAFME) is an autosomal dominant disorder characterized by adult-onset cortical tremor or action myoclonus predominantly in the upper limbs, and generalized seizures. We investigated a Thai BAFME family. Clinical and electrophysiological studies revealed that 13 were affected with BAFME. There were a total of 24 individuals studied. Genetic analysis by genome-wide linkage study (GWLS) was performed using 400 microsatellite markers and excluded linkage of the previous BAFME loci, 8q23.3-q24.1, and 2p11.1-q12.2. GWLS showed that the disease-associated region in our Thai family was linked to a newly identified locus on chromosome 3q26.32-3q28. This locus represents the fourth chromosomal region for BAFME.

Simultaneous representation of sensory and mnemonic information in human visual cortex

Traversing sensory environments requires keeping relevant information in mind while simultaneously processing new inputs. Visual information is kept in working memory via feature selective responses in early visual cortex, but recent work had suggested that new sensory inputs wipe out this information. Here we show region-wide multiplexing abilities in classic sensory areas, with population-level response patterns in visual cortex representing the contents of working memory concurrently with new sensory inputs.

Relief from intractable phantom pain by combining psilocybin and mirror visual-feedback (MVF)

ABSTRACT AL’s leg was amputated resulting in phantom-limb pain (PLP). (1) When a volunteer placed her foot on or near the phantom – touching it evoked organized sensations in corresponding locations on AL’s phantom. (2) Mirror-visual-feedback (MVF) relieved PLP, as did, “phantom massage”. (3) Psilocybin-MVF pairing produced synergistic effects, complete elimination of PLP, and reduction in paroxysmal episodes. (4) Touching the volunteer’s leg where AL previously had external fixators, evoked sensation of nails boring through the leg. Using a “telescoping” nail, we created the illusion of a nail being removed with corresponding pain relief. (5) Artificial flames produced warmth in the phantom.

Effect of Grouping, Segmentation, and Vestibular Stimulation on the Autokinetic Effect:

We report some new observations on what could be regarded as the world’s simplest visual illusion—the autokinetic effect. When a single dim spot of light is viewed in a completely dark room, it moves vividly in random directions. During steady fixation, perhaps subtle eye movements cause the image to move and a failure to correct for this using eye movement command signals leads to motion perception. This is especially true because eye muscle fatigue can lead to miscalibration. However, if two dots are shown, they often move independently in different directions, which negate the eye movement theory. In addition, two lines defining a single cross sometimes uncouple and slide past each other and the fragments composing a hidden object move independently until they click in place and the whole object is perceived—implying that the illusion occurs relatively late in visual processing. Finally, the effect is modulated by vestibular stimulation; anchoring your sense of self may be a prerequisite for binding features into coherent objects.

Trigger Features for Conveying Facial Expressions: The Role of Segmentation

Primates are especially good at recognizing facial expression using two contrasting strategies—an individual diagnostic feature (e.g., raise eyebrows or lower mouth corner) versus a relationship between features. We report several novel experiments that demonstrate a profound role of grouping and segmentation—including stereo—on recognition of facial expressions.

Calendars in the brain; their perceptual characteristics and possible neural substrate

ABSTRACT When we visualize a calendar, we have a vague impression of a rectangular grid hovering in front. But 1% of the population “see” vivid, crisp “calendar form” – e.g. an odd V shape as in subject ML. We found that (1) ML could “read off”, months of her calendar – or alternate months – backward, unlike controls; (2) her eyes and index finger unconsciously “tracked” her reading; (3) her calendar moved with her gaze and tilted with her head; (4) after looking at a contracting spiral, her calendar expanded. In a second subject EA, the calendar was body centered and the access to episodic memories was partially “blocked” when she “looked away”. Our experiments provide, for the first time, clear unambiguous proof for the veracity and true perceptual nature of the phenomenon. We suggest the calendar is constructed in the angular gyrus and its connections with the hippocampus via the inferior longitudinal fasciculus.