Joyce Chen ’23
Biological organisms are naturally stimulated by their environment. To avoid being overstimulated, animals use selective attention. By simply focusing on one thing, humans and other animals can essentially drown out other irrelevant stimuli. This phenomenon requires sensory regulation, especially auditory. To gain insight on how auditory neurons react to both irrelevant and target stimuli, Stony Brook University researcher Pan-tong Yao and his team of four used mice as models.
The mice were placed in a dark sound-proof chamber consisting of built-in speakers for sound delivery, infrared phototransistors to measure the mice’s reactions, water as rewards, and two LED sensors that the mice had to prod in order to begin and end each trial. For the trials, a visual stimulus would flash and signal the correct sensor that would lead to reward. From that stimulus, the mice determined which sensor to poke to receive water. An auditory stimulus was also utilized in the trials. It was presented at frequencies ranging from 5 to 40 kHz, containing many overlapping noises and tones. These stimuli were categorized into two groups: the low stimulus ranged from 5 to 10 kHz, whereas the high stimulus ranged from 20 to 40 kHz. The mice were required to distinguish between the low and high frequencies by prodding the appropriate sensor. After 4 weeks, most of the mice had practically mastered how to perform the tasks with a 90% accuracy level or higher.
The team then proceeded to inject AAV9-calmodulin protein kinase II into the auditory cortex of the brain, later placing a probe and a base plate to properly scan and analyze calcium signaling images. The scanned results highlighted how the auditory stimuli targeted different auditory neurons within the mice brains. They found that focusing on a task required the activation of both attended and unattended sensory neurons and areas of the brain, though different ones are stimulated depending on the attentiveness of the mouse.
Dr. Yao and his research team’s experiment demonstrate how vital of a role sensory neurons undertake when modulated in the brain during active stimuli. This is a revolutionary collection of data that will aid in investigations on the effects of target stimuli on responsive neurons, resulting in particular behaviors in animals and humans. Future research will be conducted to look into stimulus-nonresponsive neurons.
 P. Yao, et al., Cortical ensemble activity discriminates auditory attentional states. Mol Brain 12, 80 (2019). Doi: 10.1186/s13041-019-0502-z
Tags: #sensoryneurons #stimuli #sensoryregulation