Seyed Javad Saghravanian

All Publications

• 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