Banca de DEFESA: LUCAS DE MELO LIRA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : LUCAS DE MELO LIRA
DATE: 25/09/2026
TIME: 09:30
LOCAL: https://meet.google.com/rej-pmhd-njj
TITLE:

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

KEY WORDS:

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

PAGES: 95
BIG AREA: Ciências Biológicas
AREA: Fisiologia
SUMMARY:

The precise timing of neuronal responses has been proposed as a coding mechanism in the visual system. In the retina and the retinogeniculate system, the expression of fast rhythms and neuronal synchronization is strongly modulated by the level and type of anesthesia, requiring periodically evoked responses and intrinsically generated oscillations to be analyzed separately (Neuenschwander et al., 2023). In this study, we investigated how the entrainment of neuronal responses to periodic visual stimulation reveals underlying synchronization phenomena in the  retina and lateral geniculate nucleus (LGN) of anesthetized cats. We developed a custom visual stimulation system that combined a concentric LED array with an equivalent stimulus presented on an OLED monitor. Both systems were organized into independently addressable stimulation regions, allowing precise control of flicker frequency, luminance level, phase, and duty cycle. The stimulus consisted of a central element surrounded by independently controllable annular sectors. Using this system, we observed robust periodic responses that were temporally locked to the stimulation. These responses shared properties previously described for intrinsic gamma activity, including their dependence on stimulus extent and intensity. Entrained rhythms were tested at frequencies of up to 120 Hz. Responses to the
stimuli substantially exceeded the temporal resolution classically described for X and Y cells in the cat LGN (Lehmkuhle et al., 1980). Disrupting the radial continuity of the stimulus through spatial or temporal discontinuities, or through phase shifts in the flickering surround and peripheral regions, impaired entrainment. These results suggest that the entrainment of retinal ganglion cell responses depends on an active mechanism of population synchronization and may operate according to principles similar to those proposed for visual binding. Thus, the functional significance may arise not from the oscillations themselves, but from the precise synchronization of neuronal activity. More broadly, our findings indicate that the entrainment of LGN neurons reflects a population-level process that is sensitive to the spatial and temporal organization of visual stimulation.

COMMITTEE MEMBERS:
Externo à Instituição - ESTÊVÃO CARLOS LIMA - USP
Externo à Instituição - JEROME PAUL ARMAND LAURENT BARON - UFMG
Interno - 1698305 - RODRIGO NEVES ROMCY PEREIRA
Presidente - 1842426 - SERGIO TULIO NEUENSCHWANDER MACIEL
Interno - 2183828 - TARCISO ANDRE FERREIRA VELHO