Banca de QUALIFICAÇÃO: LUCAS DE MELO LIRA

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : LUCAS DE MELO LIRA
DATE: 27/04/2026
TIME: 14:00
LOCAL: https://meet.google.com/pch-tmnm-qrs
TITLE:

Gamma Resonances: Propagation of Periodic Neural Signals in the Retinogeniculate Cortical System

KEY WORDS:

Neuronal entrainment; Population synchronization; Retina; Lateral geniculate nucleus (LGN); Periodic visual stimulation.

 

PAGES: 57
BIG AREA: Ciências Biológicas
AREA: Fisiologia
SUMMARY:

The precise timing of neuronal responses has been proposed as a coding mechanism in the visual system (Meister, 2025). In the retina, this mechanism has been associated with gamma-band oscillations, but these rhythms depend critically on the level and type of anesthesia, particularly halothane and isoflurane (Neuenschwander et al., J. Neurosci., 2023). Here, we investigated how the entrainment of neuronal responses to periodic visual stimulation reveals underlying synchronization phenomena in the retina and the lateral geniculate nucleus (LGN) of the anesthetized cat. We developed a custom visual stimulation device based on a concentric LED array combined with an equivalent stimulus presented on an OLED monitor. Both are organized into groups of independently addressable stimuli, allowing precise control of flicker frequency, luminance amplitude, phase, and duty cycle. This stimulation consists of a central element surrounded by independently controllable annular sectors, each allowing precise control of flicker frequency, luminance amplitude, phase, and duty cycle. Using this system, we found robust entrainment of responses to periodic inputs under ketamine and propofol. This entrainment shares key properties with intrinsic gamma oscillations, including dependence on stimulus size and intensity. The peak frequencies of the intrinsic rhythms (3 cats, 60 recording sites; mean of 80 Hz, maximum of 118 Hz) and of the entrained rhythms (tested up to 120 Hz) reached values far above the temporal resolution of X and Y cells in the cat LGN (12 and 20 cycles/s, respectively; Lehmkuhle et al., J. Neurophysiol., 1980). Disrupting the radial continuity of the stimulus, whether through spatial or temporal discontinuities or through phase rotations in flickering surround and peripheral stimuli, abolished entrainment. These results suggest that entrainment of retinal ganglion cell responses depends on an active mechanism of population synchronization and may follow the same principles
as visual binding. The implication is that, at the retinal level, it is not the oscillations themselves that have functional significance, but rather the synchronization of neuronal activity, indicating that, at the retinal level, it is not the oscillations per se, but their synchronization, that is functionally significant. These findings indicate that entrainment of retina/LGN neurons depends on an active mechanism of population synchronization, potentially operating according to principles similar to those proposed for visual binding. Thus, at the retinal level, functional significance does not arise from the oscillations themselves, but from the precise synchronization of neuronal activity.

 

COMMITTEE MEMBERS:
Externo à Instituição - JEROME PAUL ARMAND LAURENT BARON - UFMG
Interna - 1871878 - KERSTIN ERIKA SCHMIDT
Presidente - 1842426 - SERGIO TULIO NEUENSCHWANDER MACIEL