Neuroimaging: mania, revolution, or technological evolution? - A critical review

Imaging has become an increasingly important tool in both research and clinical care. A range of neuroimaging technologies provide unprecedented sensitivity to visualisation of brain structure (i.e. anatomy) and function (i.e. physiology) from the level of individual molecules to the whole brain. Many imaging methods are non-invasive and allow dynamic processes to be monitored over time. Imaging is enabling researchers to identify neural networks involved in cognitive processes; understand disease pathways; recognise and diagnose diseases early, when they are most effectively treated; and determine how therapies work. The cognitive neuroscience of higher order auditory processing has advanced enormously in a brief time, in large part benefiting from neuroimaging approaches. A significant amount of progress has been made, and much of it can be attributed to the possibilities for crossing boundaries afforded by neuroimaging tools. More sophisticated experiments combined with fMRI and EEG are helping to know what the brain is doing as people perform cognitive, emotional, and behavioural actions. MEG technology will allow linguists to explore how social interaction and sensorimotor experience affects the cortical processing of language in children; and the combination of behavioural and brain measures may enhance the certainty with which dyslexia can be predicted for a child and promote the possibility of preventive intervention

Valence-specific Enhancements in Visual Processing Regions Support Negative Memories:

Thesis advisor: Elizabeth A. KensingerResearch in four parts examines the effects of valence on the neural processes that support emotional memory formation and retrieval. Results show a consistent valence-specific enhancement of visuocortical engagement along the ventral visual stream and occipital cortex that supports negative memories to a greater extent than positive memories. Part I investigated the effects of valence on the interactions between trial-level physiological responses to emotional stimuli (i.e., heart rate deceleration) during encoding and subsequent memory vividness. Results showed that negative memory vividness, but not positive or neutral memory vividness, is tied to arousal-related enhancements of amygdala coupling with early visual cortex during encoding. These results suggest that co-occurring parasympathetic arousal responses and amygdala connectivity with early visual cortex during encoding influence subsequent memory vividness for negative stimuli, perhaps reflecting enhanced memory-relevant perceptual enhancements during encoding of negative stimuli. Part II examined links between individual differences in post-encoding increases is amygdala functional connectivity at rest and the degree and direction of emotional memory biases at retrieval. Results demonstrated that post-encoding increases in amygdala resting state functional connectivity with visuocortical and frontal regions predicted the degree of negative memory bias (i.e., better memory for unpleasant compared to pleasant stimuli) and positive memory bias, respectively. Further, the effect of amygdala-visuocortical post-encoding coupling on behavioral negative memory bias was completely mediated by greater retrieval-related activity for negative stimuli in visuocortical areas. These findings suggest that those individuals with a negative memory bias tend to engage visual processing regions across multiple phases of memory more than individuals with a positive memory bias. While Parts I-II examined encoding-related memory processes, Part III examined the effects of valence on true and false subjective memory vividness at the time of retrieval. The findings showed valence-specific enhancements in regions of the ventral visual stream (e.g., inferior temporal gyrus and parahippocampal cortex) support negative memory vividness to a greater extent than positive memory vividness. However, activation of the parahippocampal cortex also drove a false sense of negative memory vividness. Together, these findings suggest spatial overlap in regions that support negative true and false memory vividness. Lastly, Part IV utilized inhibitory repetitive transcranial magnetic stimulation (rTMS) to test if a portion of occipito-temporal cortex that showed consistent valence-specific effects of negative memory in Parts I-III was necessary for negative memory retrieval. Although some participants showed the hypothesized effect, there was no group-level evidence of a neuromodulatory effect of occipito-temporal cortex rTMS on negative memory retrieval. Together, the results of the current dissertation work highlight the importance of valence-based models of emotional memory and consistently implicated enhanced visuosensory engagement across multiple phases of memory. By identifying valence-specific effects of trial-level physiological arousal during encoding, post-encoding amygdala coupling during early consolidation, and similarities and differences between true and false negative memories, the present set of work has important implications for how negative and positive memories are created and remembered differently.Thesis (PhD) — Boston College, 2019.Submitted to: Boston College. Graduate School of Arts and Sciences.Discipline: Psychology

The functional anatomy of white matter pathways for visual configuration learning

The role of the medial temporal lobes (MTL) in visuo-spatial learning has been extensively studied and documented in the neuroscientific literature. Numerous animal and human studies have demonstrated that the parahippocampal place area (PPA), which sits at the confluence of the parahippocampal and lingual gyri, is particularly important for learning the spatial configuration of objects in visually presented scenes. In current visuo-spatial processing models, the PPA sits downstream from the parietal lobes which are involved in multiple facets of spatial processing. Yet, direct input to the PPA from early visual cortex (EVC) is rarely discussed and poorly understood. This thesis adopted a multimodal neuroimaging analysis approach to study the functional anatomy of these connections. First, the pattern of structural connectivity between EVC and the MTL was explored by means of surface-based ‘connectomes’ constructed from diffusion MRI tractography in a cohort of 200 healthy young adults from the Human Connectome Project. Through this analysis, the PPA emerged as a primary recipient of EVC connections within the MTL. Second, a data-driven clustering analysis of the PPA’s connectivity to an extended cortical region (including EVC, retrosplenial cortex, and other areas) revealed multiple clusters with different connectivity profiles within the PPA. The two main clusters were located in the posterior and anterior portions of the PPA, with the posterior cluster preferentially connected to EVC. Motivated by this result, virtual tractography dissections were used to delineate the medial occipital longitudinal tract (MOLT), the white matter bundle connecting the PPA with EVC. The properties of this bundle and its relation to visual configuration learning were verified in a different, cross-sectional adult cohort of 90 subjects. Finally, the role of the MOLT in the visuo-spatial learning domain was further confirmed in the case of a stroke patient who, after bilateral occipital injury, exhibited deficits confined to this domain. The results presented in this work suggest that the MOLT should be included in current visuo-spatial processing models as it offers additional insight into how the MTL acquires and processes information for spatial learning

Multimodal MRI characterization of visual word recognition: an integrative view

228 p.The ventral occipito-temporal (vOT) association cortex contributes significantly to recognize different types of visual patterns. It is widely accepted that a subset of this circuitry, including the visual word form area (VWFA), becomes trained to perform the task of rapidly identifying word forms. An important open question is the computational role of this circuitry: To what extent is part of a bottom-up hierarchical processing of information on visual word recognition and/or is involved in processing top-down signals from higher-level language regions. This doctoral dissertation thesis proposal is aimed at characterizing the vOT reading circuitry using behavioral, functional, structural and quantitative MRI indexes, and linking its computations to the other two important regions within the language network: the posterior parietal cortex (pPC) and the inferior frontal gyrus (IFG). Results revealed that two distinct word-responsive areas can be segregated in the vOT: one responsible for visual feature extraction that is connected to the intraparietal sulcus via the vertical occipital fasciculus and a second one responsible for semantic processing that is connected to the angular gyrus via the posterior arcuate fasciculus and to the IFG via the anterior arcuate fasciculus. Importantly, reading behavior was predicted by functional activation in regions identified along the vOT, pPC and IFG, as well as by structural properties of the white matter fiber tracts linking them. The present work constitutes a critical step in the creation of a highly detailed characterization of the early stages of reading at the individual-subject level and to establish a baseline model and parameter range that might serve to clarify functional and structural differences between typical, poor and atypical readers.BCBL: basque center on cognition, brain and languag