Development of a neural circuit in the superior colliculus: analysis of the propagation of neuronal excitation from intermediate to superficial layers.

The superior colliculus is important for orientation behaviors, in which visuomotor transformation is performed by the pathway from the superficial layer (SGS) to the intermediate layers (SGI). The opposite pathway (from the SGI to the SGS) also exists, raising the possibility of a feedback circuit, although it could be either negative (inhibitory) or positive (excitatory). In this study, we focused on the development of the feedback circuit.

[Development of a cognitive BMI "neurocommunicator" as a communication aid of patients with severe motor deficits].

A cognitive brain-machine interface (BMI), "neurocommunicator" has been developed by the author's research group in AIST in order to support communication of patients with severer motor deficits. The system can identify candidate messages (pictograms) in real time from electroencephalography (EEG) data, combining three core technologies; 1) a portable/wireless EEG recorder; 2) a high-speed and high-accuracy decoding algorithm; and 3) a hierarchical message generation system. The accuracy of the model at single predictions of the target was generally over 95%, corresponding to about 32 bits per minute for normal subjects.

Inhibition in superior colliculus neurons in a brightness discrimination task?

Simultaneous recordings were collected from between two and four buildup neurons from the left and right superior colliculi in rhesus monkeys in a simple two-choice brightness discrimination task. The monkeys were required to move their eyes to one of two response targets to indicate their decision. Neurons were identified whose receptive fields were centered on the response targets.

Neural mind reading of multi-dimensional decisions by monkey mid-brain activity.

Brain-machine interfaces (BMIs) have the potential to improve the quality of life for individuals with disabilities. We engaged in the development of neural mind-reading techniques for cognitive BMIs to provide a readout of decision processes. We trained 2 monkeys on go/no-go tasks, and monitored the activity of groups of neurons in their mid-brain superior colliculus (SC).

Dual diffusion model for single-cell recording data from the superior colliculus in a brightness-discrimination task.

Monkeys made saccades to one of two peripheral targets based on the brightness of a central stimulus. Task difficulty was manipulated by varying the ratio of stimulus black-and-white pixels. Correct response probability for two monkeys varied directly with difficulty.

Single trial-based prediction of a go/no-go decision in monkey superior colliculus.

While some decision-making processes often result in the generation of an observable action, for example eye or limb movements, others may prevent actions and occur without an overt behavioral response. To understand how these decisions are made, one must look directly at their neuronal substrates. We trained two monkeys on a go/no-go task which requires a saccade to a peripheral cue stimulus (go) or maintenance of fixation (no-go).

Prefrontal neurons coding suppression of specific saccades.

The prefrontal cortex has been implicated in the suppression of unwanted behavior, based upon observations of humans and monkeys with prefrontal lesions. Despite this, there has been little direct neurophysiological evidence for a mechanism that suppresses specific behavior. In this study, we used an oculomotor delayed match/nonmatch-to-sample task in which monkeys had to remember a stimulus location either as a marker of where to look or as a marker of where not to look.

Neurons in monkey prefrontal cortex whose activity tracks the progress of a three-step self-ordered task.

The self-ordered task is a powerful tool for the analysis of dorsal prefrontal deficits. Each trial consists of a number of steps, and subjects must remember their choices in previous steps. The task becomes more difficult as the number of objects to be remembered increases.