Biology subjects

Flick, G.

Publications and source records attributed to Flick, G..

5 recordsLinked to original sources

bioRxiv2025

Phase-locking saccades to posterior alpha oscillations improves the neural representation of visual objects during memory formation

Visual memory formation begins with the intake and neural processing of discrete samples provided by gaze fixations and saccades. Past research has highlighted a functional relationship between the timing of saccades and oscillations in neural activity over posterior brain areas: saccades phase-lock to alpha oscillations (8-12 Hz) and the degree of phase-locking, in natural scenes, has been associated with subsequent recognition memory. Here, we tested the hypothesis that the putative memory encoding benefit arises due to improved neuronal processing and, ultimately, better neural representation of foveated items, when saccades are locked to alpha phase. In a co-registered magnetoencephalography (MEG) and eye-tracking paradigm, participants executed saccades from central fixation to images that appeared in the periphery, attempting to remember those images for later testing. Replicating past results, saccades to subsequently remembered images were preceded by greater inter-trial phase coherence in the alpha frequency band, at posterior MEG channels, consistent with the notion that the eye movements were phase-locked. Across participants, the degree of saccade phase-locking was positively correlated with how well visual and semantic properties of the images were represented in neural activity, within 200 ms of their foveation. This relationship was evident in responses localized to the left parieto-occipital and ventral temporal cortex, where greater saccade phase-locking was associated with improved visual and semantic representations, respectively. These results support the hypothesis that phase-locking saccades to alpha oscillations leads to improved neuronal representation of foveated stimuli, providing new mechanistic insight into how episodic memories are formed from discrete visual samples. Significance StatementVisual memories begin with discrete samples provided by eye movements and gaze fixations, from which the brain must extract information that is integrated into a coherent memory trace. This work examined the neural mechanisms that support this memory formation process, one eye movement at a time. The results identified a functioning coupling between saccade timing and neuronal oscillations in the alpha frequency band: when saccades are phase-locked to alpha oscillations, the brain can better process the visual information provided by gaze fixations. This indicates that precise coordination of saccade timing, with respect to neuronal oscillations, promotes more veridical neural representation of the resulting visual samples, from which accurate episodic memories can be constructed.

neuroscience↗

bioRxiv2025

Reading ahead: Localized neural signatures of parafoveal word processing and skipping decisions

Visual reading proceeds fixation-by-fixation, with individual words recognized and integrated into evolving conceptual representations within only hundreds of milliseconds. This relies, in part, on interactions between cognitive and oculomotor systems, such that linguistic properties of words influence eye movements and fixation durations. When and where do these influences arise in the neural processing of an incoming word? To answer this, we combined magnetoencephalography (MEG) with eye-tracking in a natural story-reading paradigm. We replicated past findings that word frequency and predictability have additive influences on fixation durations. Next, we identified putative generators of these influences in localized brain activity time-locked to fixation onsets. Both properties independently influenced neural responses in left occipitotemporal and ventral temporal areas, at latencies early enough to influence subsequent saccade planning. These effects began in posterior areas (the left lingual gyrus, lateral occipital cortex) during parafoveal word processing, and shifted more anteriorly (the inferior temporal and parahippocampal gyri) when the word was fixated in foveal vision. Evidence for parallel processing of both parafoveal and foveal words was observed in the left posterior fusiform, which housed near-simultaneous effects of both the fixated and upcoming words frequency and surprisal. We also found that parafoveal processing in this region, together with the left middle temporal gyrus, distinguished whether an upcoming word was skipped or fixated. These results suggest that during natural visual reading, word recognition and integration begin parafoveally, underpinned by a left-lateralized occipitotemporal system, where word processing rapidly exerts downstream influences on eye movement decisions.

neuroscience↗

bioRxiv2022

Global Motor Inhibition Precedes Stuttering Events

Research points to neurofunctional differences underlying fluent speech between stutterers and non-stutterers. Considerably less work has focused on processes that underlie stuttered vs. fluent speech. Additionally, most of this research has focused on speech motor processes despite contributions from cognitive processes that occur prior to the onset of stuttered speech. We used MEG to test the hypothesis that reactive inhibitory control is triggered prior to stuttered speech. Twenty-nine stutterers completed a delayed-response task that featured a cue (prior to a go cue) signaling the imminent requirement to produce a word that was either stuttered or fluent. Consistent with our hypothesis, we observed increased beta power in the R-preSMA -an area implicated in reactive inhibitory control- in response to the cue preceding stuttered vs. fluent productions. Beta power differences between stuttered and fluent trials correlated with stuttering severity and participants percentage of trials stuttered increased exponentially with beta power in the R-preSMA. Trial-by-trial beta power modulations in the R-preSMA following the cue predicted whether a trial would be stuttered or fluent. Stuttered trials were also associated with delayed speech onset suggesting an overall slowing or freezing of the speech motor system that may be a consequence of inhibitory control. Post-hoc analyses revealed that independently-generated anticipated words were associated with greater beta power and more stuttering than researcher-assisted anticipated words, pointing to a relationship between self-perceived likelihood of stuttering (i.e., anticipation) and inhibitory control. This work offers a neurocognitive account of stuttering by characterizing the cognitive processes that precede overt stuttering events.

neuroscience↗

bioRxiv2020

From letters to composed concepts: A magnetoencephalography study of reading

Language comprehension requires the recognition of individual words and the combination of their meanings to yield complex concepts or interpretations. Rather than simple concatenation, this combinatory process often requires the insertion of unstated semantic material between words, based on thematic or feature knowledge of the concepts. For example, the phrase horse barn is not interpreted as a blend of a horse and a barn, but specifically a barn in which horses are kept. Mounting evidence suggests two cortical semantic hubs, in left temporoparietal and anterior temporal cortex, underpin thematic and feature concept knowledge, but much remains unclear about how these putative hubs contribute to combinatory language processing. Using magnetoencephalography, we contrasted source-localized responses to modifier-noun phrases involving thematic relations vs. feature modifications, while also examining how lower-level orthographic processing fed into responses supporting word combination. Twenty-eight participants completed three procedures examining responses to letter-strings, adjective-noun phrases, and noun-noun combinations that varied the semantic relations between words. We found that while color + noun phrases engaged the left anterior temporal lobe (150-300 ms after phrasal head), posterior temporal lobe (150-300 ms), and angular gyrus (300-450 ms), only left posterior temporal lobe responses were sensitive to implicit thematic relations between composing nouns (150-300 ms). We additionally identified a left temporo-occipital progression from orthographic to lexical processing, feeding into ventral anterior areas engaged in the combination of word meanings. Finally, by examining source signal leakage, we characterized the degree to which these responses could be distinguished from one another, using linear source estimation.

neuroscience↗

bioRxiv2018

Isolating syntax in natural language: MEG evidence for an early contribution of left posterior temporal cortex

Syntax is the engine that allows us to create an infinitude of linguistic expressions, and the construction of syntactic structures, such as noun phrases and verb phrases, is considered a fundamental component of language processing. Nevertheless, insights concerning the neurobiological basis of syntax have remained elusive, in part because it is difficult to isolate syntax from semantic composition. Consequently, many studies of syntax have relied on meaningless artificial stimuli, such as jabberwocky expressions or artificial grammars. However, while pure manipulations of syntax are challenging to design, natural language grammars do have a sparse set of constructions presenting this possibility. Here we examined one such case, English post-nominal adjectives (mountain TALL enough for a strenuous hike), which were contrasted with semantically parallel but structurally simpler noun-adjective sequences in an MEG experiment. We observed a sharp activity increase in the left posterior temporal lobe (PTL) when syntactic composition was more straightforward, approximately 200 ms after adjective onset. The semantic fit between the noun and adjective was also varied, but this affected anterior temporal cortex, consistent with prior work. These findings offer a unique demonstration of the relevance of posterior temporal cortex for syntactic processing in natural language. We also present connectivity evidence that the syntax-related PTL responses were relayed to ipsilateral inferior frontal and anterior temporal regions. The combined results draw an initial picture of the rapid spatio-temporal dynamics of the syntactic and semantic composition network in sentence processing.

neuroscience↗