مجيد روشنائي

This study investigates the impact of working memory on visual processing in the middle temporal (MT) area of the brain. To achieve this, two advanced analytical methods—Maximal Overlap Discrete Wavelet Transform (MODWT) an‎d Inter-Trial Coherence (ITC)—were applied to neural activity data recorded from rhesus monkeys performing a spatial working memory task. Findings from the MODWT analysis revealed that working memory selec‎tively alters the parameters of neural oscillations. The presence of a memory signal not only increased the power of low-frequency waves but also shifted the dominant frequency of these oscillations to higher values, particularly when the memory content overlapped with the neuronʹs receptive field. A strong correlation was observed between oscillation frequency an‎d neuronal firing rates, such that higher frequencies were associated with greater neuronal activity. This suggests a fundamental link between the mechanisms generating brain rhythms an‎d the level of neuronal activity. Additionally, working memory enhanced the quality of spatial information encoding by embedding information more precisely within the phase of neural oscillations. The ITC analysis uncovered another complementary mechanism: working memory can influence the timing of sensory processing even before changes in neuronal firing rates occur. When the content held in working memory matched the center of a neuronʹs receptive field, visual signals reached the MT area earlier. This acceleration was measured by increased phase coherence in neural responses an‎d indicates an optimization of processing by working memory. This effect was location-dependent, as focusing memory on locations distant from the receptive field center not only failed to produce acceleration but could sometimes lead to processing delays. In summary, these findings reveal a dual mechanism for working memory modulation: spectral tuning through changes in the power an‎d frequency of neural oscillations, an‎d temporal acceleration through enhanced phase coherence. These complementary processes strengthen sensory representation during working memory tasks an‎d optimize both the spectral an‎d temporal characteristics of neural processing.

حافظه كاري , ناحيه گيجگاهي مياني , پتانسيل ميدان محلي , تبديل موجك گسسته با بيشينه همپوشاني , كوهيرنس بين آزمايش

working memory , middle temporal , local field potential , maximal overlap discrete wavelet transform , inter trial coherence

majid roshanaei

mahmmod reza daliri