Biology subjects

Toledano, R.

Publications and source records attributed to Toledano, R..

3 recordsLinked to original sources

bioRxiv2025

Emotional amnesia in humans with focal temporal pole lesions

Memory is typically better for emotional relative to neutral events, a process involving amygdala modulation of hippocampal activity1-6. These structures, however, form part of a larger emotional brain network, which in humans includes the temporal pole7, a cortical node whose functional role in emotional cognition remains poorly understood8-10. Here, we show, in pharmaco-resistant epilepsy patients performing verbal and visual emotional episodic memory tasks, a selective impairment in recalling verbal emotional memories in left ventral temporal pole (vTP) lesioned patients compared with control patients. Memory for neutral words, and verbal comprehension performance on standard neuropsychological testing, were intact in these patients, indicating absence of general episodic memory or semantic impairment. All patients underwent recordings with intracranial electrodes during memory task performance. Left vTP lesioned patients showed no differences in amygdala or hippocampal electrophysiological responses to emotional words, compared with control patients, putatively isolating a vTP role in emotional memory. Unlike verbal emotional recall, left vTP lesioned patients showed memory enhancement for emotional vs. neutral pictures, whereas two patients with right vTP lesions showed the opposite pattern: impaired memory for emotional pictures but intact verbal emotional memory. These observations establish a critical, lateralized, modality-specific role for human vTP in emotional memory, imply emotional memory deficits in neurological conditions affecting this region, and advance the vTP as a target for neuromodulation in diseases characterized by maladaptive emotional memories.

neuroscience↗

bioRxiv2024

Retrieval of human aversive memories involves reactivation of gamma activity patterns in the hippocampus that originate in the amygdala during encoding

Emotional memories require coordinated activity of the amygdala and hippocampus. Human intracranial recordings have shown that formation of aversive memories involves an amygdala theta-hippocampal gamma phase code. Yet, the mechanisms engaged during translation of aversive experiences into memories and subsequent retrieval remain unclear. Directly recording from human amygdala and hippocampus, here we show that hippocampal gamma activity increases for correctly remembered aversive scenes, while exerting unidirectional oscillatory influence within the theta/beta frequency range on the amygdala for previously seen aversive scenes. Crucially, patterns of amygdala high amplitude gamma activity at encoding are reactivated in the hippocampus, but not amygdala, during both aversive encoding and retrieval. Trial-specific hippocampal gamma patterns showing highest representational similarity with amygdala activity at encoding are replayed in the hippocampus during aversive retrieval. This reactivation process occurs against a background of gamma activity that is otherwise decorrelated between encoding and retrieval. Thus, retrieval of aversive memories is hippocampal-centered, with hippocampal activity patterns apparently entrained by the amygdala during encoding.

neuroscience↗

bioRxiv2023

Human hippocampal ripples tune cortical responses in uncertain visual contexts

To be able to encode information efficiently, our perceptual system should detect when situations are unpredictable (i.e., informative), and modulate brain dynamics to prepare for encoding. Here we show, with direct recordings from the human hippocampus and visual cortex, that after exposure to unpredictable visual stimulus streams, hippocampal ripple activity increases in frequency and duration prior to stimulus presentation, indicating context and experience-dependent prediction of predictability. Pre-stimulus hippocampal ripples suppress changes in visual (occipital) cortex gamma activity associated with uncertainty, and modulate post-stimulus prediction error gamma responses in higher-level visual (fusiform) cortex to surprising (i.e., unpredicted) stimuli. These results link hippocampal ripples with predictive coding accounts of neuronal message passing--and precision-weighted prediction errors--revealing a mechanism relevant for perceptual synthesis and subsequent memory encoding.

neuroscience↗