Validation of the Tactual Span in individuals with congenital and acquired blindness

Neuropsychological assessment tools for individuals with blindness are relatively scarce. In the current study, we assessed the validity of the Tactual Span, a task aimed at evaluating tactile working memory. During the task, the fingers of both hands are touched in specific sequences of ascending difficulty, which participants are asked to repeat in exact and reverse order. Twelve participants with congenital blindness and 13 with acquired blindness were examined alongside 18 sighted controls, matched to the experimental group with respect to age and education. Participants performed the Tactual Span and three additional tasks assessing working memory in the auditory modality, as well as a Semantic Fluency test. Results showed that the Tactual Span was significantly correlated with most of the other working memory measures, in all groups, but not with the Semantic Fluency test. In addition, the congenital and acquired blindness groups performed similarly to one another and better than sighted controls on most working memory tasks, but not on the Semantic Fluency test. Findings suggest that the Tactual Span is a feasible task for measuring tactile working memory in individuals with congenital and acquired blindness. Therefore, it can expand the cognitive assessment toolbox of professionals working with blind individuals and increase the strength of conclusions drawn from cognitive assessments in educational and vocational settings.

Improving Visual Working Memory With Training on a Tactile Orientation Sequence Task in Humans

Working memory refers to the cognitive capacity to temporarily store and manipulate information from multiple sensory domains. Recent studies have shown that cognitive training can improve performance in both visual working memory and tactile working memory tasks. However, it is still unclear whether the effects of training can be transferred from one sensory modality to another. The current study assessed whether the training effect of the tactile orientation sequence task could transfer to visual orientation sequence and visuospatial working memory tasks. The results showed that participants’ accuracy in the tactile orientation sequence task was significantly increased after 9 days of training compared with that before training. Remarkably, participants’ accuracy in both the visual orientation sequence task and the visuospatial task was significantly improved after 9 days of training. These results suggest that it is possible to improve visual working memory through a transfer effect from tactile task training without practice in the visual domain, which opens a wide range of applications for tactile orientation sequence tasks.

Dense Functional and Molecular Readout of a Circuit Hub in Sensory Cortex

ABSTRACTInformation processing in the neocortex is carried out by neuronal circuits composed of different cell types. Recent census of the neocortex using single cell transcriptomic profiling has uncovered more than 100 putative cell types which subdivide major classes of excitatory and inhibitory neurons into distinct subclasses. The extent to which this molecular classification predicts distinct functional roles during behavior is unclear. Here, we combined population recordings using two-photon calcium imaging with spatial transcriptomics using multiplexed fluorescent in situ hybridization to achieve dense functional and molecular readout of cortical circuits during behavior. We characterized task-related responses across major transcriptomic neuronal subclasses and types in layer 2/3 of primary somatosensory cortex as mice performed a tactile working memory task. We find that as neurons are segregated into increasingly discrete molecular types, their task-related properties continue to differentiate. We identify an excitatory cell type, Baz1a, that is highly driven by tactile stimuli. Baz1a neurons homeostatically maintain stimulus responsiveness during altered sensory experience and show persistent enrichment of subsets of immediately early genes including Fos. Measurements of functional and anatomical connectivity reveal that upper layer 2/3 Baz1a neurons preferentially innervate somatostatin-expressing inhibitory neurons. We propose that this connection motif reflects a sensory-driven circuit hub that orchestrates local sensory processing in superficial layers of the neocortex.

Effect of working memory load on tactile n-back task

The present study investigated the characteristics of tactile working memory using the N-Back Task. The participants (n = 16), all sighted, performed the task with working memory loads equivalent to maintaining one, two, or three letters in the working memory (N-Back 1, N-Back 2, and N-Back 3). The frequency of commission and omission errors was analyzed as a function of memory load. The results indicate an increase in the frequency of omission errors due to this factor. The working memory load did not significantly influence commission errors. In general, our results suggest that the tactile N-Back task may represent a promising method for the assessment of working memory in blind and sighted participants.

Retrospective Selection in Visual and Tactile Working Memory Is Mediated by Shared Control Mechanisms

Selective attention regulates the activation of working memory (WM) representations. Retro-cues, presented after memory sample stimuli have been stored, modulate these activation states by triggering shifts of attention to task-relevant samples. Here, we investigated whether the control of such attention shifts is modality-specific or shared across sensory modalities. Participants memorized bilateral tactile and visual sample stimuli before an auditory retro-cue indicated which visual and tactile stimuli had to be retained. Critically, these cued samples were located on the same side or opposite sides, thus requiring spatially congruent or incongruent attention shifts in tactile and visual WM. To track the attentional selection of retro-cued samples, tactile and visual contralateral delay activities (tCDA and CDA components) were measured. Clear evidence for spatial synergy effects from attention shifts in visual WM on concurrent shifts in tactile WM were observed: Tactile WM performance was impaired, and tCDA components triggered by retro-cues were strongly attenuated on opposite-sides relative to same-side trials. These spatial congruency effects were eliminated when cued attention shifts in tactile WM occurred in the absence of simultaneous shifts within visual WM. Results show that, in contrast to other modality-specific aspects of WM control, concurrent attentional selection processes within tactile and visual WM are mediated by shared supramodal control processes.

Shifts of Spatial Attention in Visual and Tactile Working Memory are Controlled by Independent Modality-Specific Mechanisms

The question whether the attentional control of working memory (WM) is shared across sensory modalities remains controversial. Here, we investigated whether attention shifts in visual and tactile WM are regulated independently. Participants memorized visual and tactile targets in a first memory sample set (S1) before encoding targets in a second sample set (S2). Importantly, visual or tactile S2 targets could appear on the same side as the corresponding S1 targets, or on opposite sides, thus, requiring shifts of spatial attention in visual or tactile WM. The activation of WM representations in modality-specific visual and somatosensory areas was tracked by recording visual and tactile contralateral delay activity (CDA/tCDA). CDA/tCDA components emerged contralateral to the side of visual or tactile S1 targets, and reversed polarity when S2 targets in the same modality appeared on the opposite side. Critically, the visual CDA was unaffected by the presence versus absence of concurrent attention shifts in tactile WM, and the tactile CDA remained insensitive to visual attention shifts. Visual and tactile WM performance was also not modulated by attention shifts in the other modality. These results show that the dynamic control of visual and tactile WM activation processes operates in an independent modality-specific fashion.