Biology subjects

Mantegna, F.

Publications and source records attributed to Mantegna, F..

3 recordsLinked to original sources

bioRxiv2022

Covariance-based Decoding Reveals Content-specific Feature Integration and Top-down Processing for Imagined Faces versus Places

When we internally generate mental images, we need to combine multiple features into a whole. Direct evidence for such feature integration during visual imagery is still lacking. Moreover, cognitive control mechanisms, including memory and attention, exert top-down influences on the perceptual system during mental images generation. However, it is unclear whether such top-down processing is content-specific or not. Feature integration and top-down processing involve short-range connectivity within visual areas, and long-range connectivity between control and visual areas, respectively. Here, we used a minimally constrained experimental paradigm wherein imagery categories were prompted using visual word cues only, and we decoded face versus place imagery based on their underlying connectivity patterns. Our results show that face and place imagery can be decoded from both short-range and long-range connections. These findings suggest that feature integration does not require an external stimulus but occurs also for purely internally generated images. Furthermore, control and visual areas exchange information specifically tailored to imagery content. TeaserDecoding visual imagery from brain connectivity reveals a content-specific interconnected neural code for internal image generation.

neuroscience↗

bioRxiv2022

Speech imagery decoding as a window to speech planning and production

Speech imagery (the ability to generate internally quasi-perceptual experiences of speech) is a fundamental ability linked to cognitive functions such as inner speech, phonological working memory, and predictive processing. Speech imagery is also considered an ideal tool to test theories of overt speech. The study of speech imagery is challenging, primarily because of the absence of overt behavioral output as well as the difficulty in temporally aligning imagery events across trials and individuals. We used magnetoencephalography (MEG) paired with temporal-generalization-based neural decoding and a simple behavioral protocol to determine the processing stages underlying speech imagery. We monitored participants lip and jaw micromovements during mental imagery of syllable production using electromyography. Decoding participants imagined syllables revealed a sequence of task-elicited representations. Importantly, participants micromovements did not discriminate between syllables. The decoded sequence of neuronal patterns maps well onto the predictions of current computational models of overt speech motor control and provides evidence for hypothesized internal and external feedback loops for speech planning and production, respectively. Additionally, the results expose the compressed nature of representations during planning which contrasts with the natural rate at which internal productions unfold. We conjecture that the same sequence underlies the motor-based generation of sensory predictions that modulate speech perception as well as the hypothesized articulatory loop of phonological working memory. The results underscore the potential of speech imagery, based on new experimental approaches and analytical methods, and further pave the way for successful non-invasive brain-computer interfaces.

neuroscience↗

bioRxiv2020

Oscillatory responses to generated and perceived rhythms

Neural oscillations have been proposed as a mechanism for structure building in language and music. In music, this idea is appealing because of the intuitive mapping between perceptual and neural rhythms. The strongest evidence has come from studies in which participants listened to isochronous sequences of identical tones and were asked to imagine hearing them in binary (march) or ternary meter (waltz). The critical finding was that in addition to increased signal at the frequency corresponding to the tone rate there was increased signal at the imagined meter frequencies. While it is striking that meter tracking was observed without any acoustic cues in the input, rhythm perception was confounded with rhythm imagery involving active generation of rhythmic structure. We conducted two electroencephalography experiments with musicians and non-musicians, teasing apart the effects of rhythm perception and rhythm generation. Evidence for meter-related neural oscillations was only observed in situations where rhythmic structure was actively generated, either via rhythm imagery or in the form of overt behavior (tapping). Thus, our data suggest that mere rhythm perception is not sufficient to elicit oscillations at the meter frequency and that they are instead driven by the active generation of rhythm. This undermines the proposal that neural oscillations constitute a basic structure building mechanism in rhythm perception and raises questions about the role of oscillations in language processing.

neuroscience↗