Seyed Javad Saghravanian

All Publications

• Evaluating the impact of intracerebroventricular norepinephrine on spatial memory in rats: Insights into sporadic Alzheimer's pathogenesis. IBRO neuroscience reports Moien, M. A., Saghravanian, S. J., Fereidoni, M. 2026; 20: 84-93

  Abstract

  One consequence of stress is the increased release of norepinephrine (NE) in the central nervous system, primarily driven by activation of the sympathetic nervous system. Given the importance of chronic stress in the development and progression of Alzheimer's disease (AD), clarifying the specific contributions of stress-related pathways, including the sympathetic axis and the hypothalamic-pituitary-adrenal (HPA) axis, is critical. In this study, we examined the effects of repeated central NE administration, as a potential contributor to stress-related cognitive impairment, on spatial memory in rats, alone or in combination with a low-dose streptozotocin (STZ) model of sporadic AD. Forty-nine rats were assigned to seven groups: control (no treatment), sham (saline; i.c.v.), low-dose streptozotocin (0.5 mg/kg, i.c.v.), norepinephrine administration at either 1 (adolescent) or 3 (adult) months of age (30 or 50 μg, respectively; i.c.v.), and co-administration of norepinephrine with streptozotocin at 1 or 3 months of age. Spatial memory was assessed using the Morris Water Maze test. Norepinephrine administration during adolescence and adulthood impaired spatial memory similar to streptozotocin in different parameters of the MWM, with adult rats showing the most significant vulnerability (p < 0.001). However, co-administration of both substances did not exacerbate the impairment caused by each alone. The results suggest that norepinephrine may impair cognition through mechanisms distinct from those of STZ-induced deficits. Additionally, they raise questions about the contribution of the sympathetic axis of chronic stress to the progression of sporadic AD.

  View details for DOI 10.1016/j.ibneur.2025.12.012

  View details for PubMedID 41550978

  View details for PubMedCentralID PMC12811423

• Transcranial direct current stimulation of the occipitotemporal cortex enhances identification of ambiguous faces. Scientific reports Saghravanian, S. J., Esteky, H. 2025

  Abstract

  Transcranial direct current stimulation (tDCS) has emerged as a promising tool for investigating the neural mechanisms underlying various brain functions and for enhancing related behavioral performance. In this sham-controlled, between-subjects study, we examined the effects of tDCS applied to the right and left occipitotemporal cortex (OTC) on face identification performance using a delayed match-to-sample task with morphed face images of varying discrimination difficulty. Three active montages were tested: (M1) anode on the right OTC and cathode on the left OTC, (M2) anode on the left OTC and cathode on the right OTC, and (M3) anode on the right OTC with the cathode on the left shoulder. A total of 47 participants were randomly assigned to one of four groups: M1 (n = 13), M2 (n = 12), M3 (n = 13), and Sham (n = 9). The results showed a significant improvement in face discrimination performance with the M1 montage relative to the sham condition. Although performance also improved in M2 and M3, these effects were not significantly different from the sham group. Across all montages, the largest impact on non-match discrimination was observed under more ambiguous conditions, particularly at a 30% morph distance, which corresponded to the point of subjective equality. Furthermore, tDCS stimulation led to longer reaction times across all montages, with the significant delays noted in M1 and M3. Findings of this preliminary study suggest a hemispheric laterality bias in face identity discrimination following tDCS-induced neural modulation.

  View details for DOI 10.1038/s41598-025-31236-2

  View details for PubMedID 41387765

• Rethinking attention: A unified perspective on top-down and bottom-up processes. Acta psychologica Saghravanian, S. J. 2025; 258: 105244

  Abstract

  Attention enables organisms to prioritize information in environments where neural and cognitive resources are limited. Traditionally, this process has been understood as the outcome of two distinct mechanisms: top-down control, shaped by goals and expectations, and bottom-up reactivity to salient stimuli. However, growing evidence from neuroscience, psychology, and evolutionary theory challenges the clarity and sufficiency of this dichotomy. This review proposes a unified framework in which attentional selection emerges from a single system guided by overlapping priorities across three timescales: evolutionary imperatives (e.g., survival), learned experiences (e.g., value-based biases), and immediate task demands. Rather than two interacting systems, top-down and bottom-up processes are reinterpreted as different temporal expressions of the same underlying mechanism. This perspective offers a reconceptualization of classical models and encourages a more integrated interpretation of neural and behavioral data.

  View details for DOI 10.1016/j.actpsy.2025.105244

  View details for PubMedID 40614431

• Acclimatizing and training freely viewing marmosets for behavioral and electrophysiological experiments in oculomotor tasks. Physiological reports Saghravanian, S. J., Asadollahi, A. 2023; 11 (3): e15594

  Abstract

  The marmoset is a small-bodied primate with behavioral capacities and brain structures comparable to macaque monkeys and humans. Its amenability to modern biotechnological techniques like optogenetics, chemogenetics, and generation of transgenic primates have attracted neuroscientists' attention to use it as a model in neuroscience. In the past decade, several laboratories have been developing and refining tools and techniques for performing behavioral and electrophysiological experiments in this new model. In this regard, we developed a protocol to acclimate the marmoset to sit calmly in a primate chair; a method to calibrate the eye-tracking system while marmosets were freely viewing the screen; and a procedure to map motor field of neurons in the SC in freely viewing marmosets. Using a squeeze-walled transfer box, the animals were acclimatized, and chair trained in less than 4 weeks, much shorter than what other studies reported. Using salient stimuli allowed quick and accurate calibration of the eye-tracking system in untrained freely viewing marmosets. Applying reverse correlation to spiking activity and saccadic eye movements, we were able to map motor field of SC neurons in freely viewing marmosets. These refinements shortened the acclimation period, most likely reduced stress to the subjects, and allowed more efficient eye calibration and motor field mapping in freely viewing marmosets. With a penetration angle of 38 degrees, all 16 channels of the electrode array, that is, all recorded neurons across SC layers, had overlapping visual receptive and motor fields, indicating perpendicular penetration to the SC.

  View details for DOI 10.14814/phy2.15594

  View details for PubMedID 36754454

  View details for PubMedCentralID PMC9908434