Age differences in fMRI adaptation for sound identity and location

We explored age differences in auditory perception by measuring fMRI adaptation of brain activity to repetitions of sound identity (what) and location (where), using meaningful environmental sounds. In one condition, both sound identity and location were repeated allowing us to assess non-specific adaptation. In other conditions, only one feature was repeated (identity or location) to assess domain-specific adaptation. Both young and older adults showed comparable non-specific adaptation (identity and location) in bilateral temporal lobes, medial parietal cortex, and subcortical regions. However, older adults showed reduced domain-specific adaptation to location repetitions in a distributed set of regions, including frontal and parietal areas, and to identity repetition in anterior temporal cortex. We also re-analyzed data from a previously published 1-back fMRI study, in which participants responded to infrequent repetition of the identity or location of meaningful sounds. This analysis revealed age differences in domain-specific adaptation in a set of brain regions that overlapped substantially with those identified in the adaptation experiment. This converging evidence of reductions in the degree of auditory fMRI adaptation in older adults suggests that the processing of specific auditory “what” and “where” information is altered with age, which may influence cognitive functions that depend on this processing

Non-Verbal Working Memory: A functional near-infrared spectroscopy (fNIRS) and functional magnetic resonance imaging (fMRI) comparison

Ulike hjernenettverk virker å bli aktivert for verbal og ikke-verbal visuell og romlig informasjon i arbeidsminnet. Det finnes et bredt spenn av forskning på det visuell-romlige arbeidsminnet. Likevel, har en tilnærming som benytter seg av objekter med flere integrerte egenskaper og en klar spesifikasjon på den verbale dimensjonen blitt mindre anvendt. Det ikke-verbale arbeidsminnet for visuell-romlig informasjon har blitt mer oversett enn det verbale arbeidsminnet. Derfor søker denne studien å adressere de nevrale nettverkene som utnyttes for ikke-verbal arbeidsminneprestasjon. Hjerneaktivitet ble målt fra totalt 12 deltagere mens de utførte en nylig komponert ikke-verbal arbeidsminneoppgave. Både funksjonell nær-infrarød spektroskopi (fNIRS) og funksjonell magnetisk resonans avbildning (fMRI) ble benyttet for formålet. Resultatene indikerte at det ikke-verbale arbeidsminnet involverer høyre-lateraliserte hjerneaktiveringer, hvor frontoparietale nettverk og visuelle traséer ble benyttet for prestasjon. Disse funnene tilbyr viktig tilførsel til den nevrale nettverksmodellen av det ikke-verbale arbeidsminnet. Dermed virker oppgaven å teste konseptet effektivt. fNIRS og fMRI ble også brukt for å måle resting-state fra de samme deltagerne. Resultatene uttrykket forskjeller mellom de to øktene ved både fMRI og fNIRS. Endringene i konnektivitet kan reflektere effekter av oppgaven på resting-state.Masteroppgave i psykologiMAPSYK360INTL-SVINTL-MEDINTL-PSYKINTL-HFINTL-KMDINTL-JUSINTL-MNMAPS-PSY

Dissociating memory networks in early Alzheimer's disease and frontotemporal lobar degeneration - a combined study of hypometabolism and atrophy

Introduction: We aimed at dissociating the neural correlates of memory disorders in Alzheimer’s disease (AD) and frontotemporal lobar degeneration (FTLD). Methods: We included patients with AD (n = 19, 11 female, mean age 61 years) and FTLD (n = 11, 5 female, mean age 61 years) in early stages of their diseases. Memory performance was assessed by means of verbal and visual memory subtests from the Wechsler Memory Scale (WMS-R), including forgetting rates. Brain glucose utilization was measured by [18F]fluorodeoxyglucose positron emission tomography (FDG-PET) and brain atrophy by voxel-based morphometry (VBM) of T1-weighted magnetic resonance imaging (MRI) scans. Using a whole brain approach, correlations between test performance and imaging data were computed separately in each dementia group, including a group of control subjects (n = 13, 6 female, mean age 54 years) in both analyses. The three groups did not differ with respect to education and gender. Results: Patients in both dementia groups generally performed worse than controls, but AD and FTLD patients did not differ from each other in any of the test parameters. However, memory performance was associated with different brain regions in the patient groups, with respect to both hypometabolism and atrophy: Whereas in AD patients test performance was mainly correlated with changes in the parieto-mesial cortex, performance in FTLD patients was correlated with changes in frontal cortical as well as subcortical regions. There were practically no overlapping regions associated with memory disorders in AD and FTLD as revealed by a conjunction analysis. Conclusion: Memory test performance may not distinguish between both dementia syndromes. In clinical practice, this may lead to misdiagnosis of FTLD patients with poor memory performance. Nevertheless, memory problems are associated with almost completely different neural correlates in both dementia syndromes. Obviously, memory functions are carried out by distributed networks which break down in brain degeneration

Review of neuroimaging in autism spectrum disorders: what have we learned and where we go from here

Autism spectrum disorder (ASD) refers to a syndrome of social communication deficits and repetitive behaviors or restrictive interests. It remains a behaviorally defined syndrome with no reliable biological markers. The goal of this review is to summarize the available neuroimaging data and examine their implication for our understanding of the neurobiology of ASD

Levels of processing and the parietal memory network

The parietal memory network (PMN) is a functional brain network that has been recently described through the convergence of task-based fMRI and resting-state functional MRI studies (Gilmore et al., 2015). The networkճ characteristic encoding/retrieval flip (deactivation at encoding and activation at later retrieval, discussed by Gilmore and colleagues) and its manifestation of a negative subsequent memory effect (greater deactivation at encoding for items that will later be recognizedѩ.e., subsequent hitsѴhan for those that will notѳubsequent misses) (Cabeza et al., 2004; Daselaar, Prince, & Cabeza, 2004; De Chastelaine & Rugg, 2014; Elman, Rosner, Cohn-Sheehy, Cerreta, & Shimamura, 2013; Kim, 2011; Otten & Rugg, 2001) and other memory-related contrasts suggest possible ties to effective encoding of memory. This study sought to use task-based functional MRI to further investigate this tie between the PMN and encoding through the use of the levels of processing paradigm (Craik & Lockhart, 1972; Craik & Tulving, 1975). Specifically, I hypothesized that the PMNѷhich demonstrates the negative subsequent memory effectѷould deactivate more for conditions that lead to more effective encoding such as a deeper level of processing. Partial support for greater deactivation in the PMN for deeper processing was observed in two of the three regions that form the network (specifically within precuneus and mid cingulate): Precuneus (and to a lesser extent) mid cingulate deactivated for deeper, semantic processing than for the more shallow orthographic processing. However, the two regions did not show differential activity between semantic and phonological processing (presumably shallower than semantic processing), despite behavioral differences; The third region of the network, PIPL, did not show a consistent levels of processing effect in the univariate analyses, nor did it show the negative subsequent memory effect despite all other PMN regions showing the effect. Linear-mixed effect modeling of PMN regions showed that trial-by-trial variation in levels of BOLD activity in precuneus and mid cingulate predicted subsequent memory, above and beyond the level of processing manipulation as well as contribution from left inferior frontal gyrus (IFG), a region consistently identified in subsequent memory studies (Kim, 2011). Attempts to use multivariate pattern analysis to classify subsequent memory using only individual PMN regions led to above chance classification (hit or miss) for all PMN regions. The ability to predict subsequent memory using only activity from PMN regions (and beyond the contribution of left IFG) supports the role of the PMN in encoding, showing that a sufficient level of deactivation in PMN regions is associated with successful encoding regardless of the level of processing. Overall, the study supported the conclusion that two members of the PMNѴhe precuneus and mid cingulateѣontribute to effective encoding of memory

Automatic and Intrinsic Auditory "What” and "Where” Processing in Humans Revealed by Electrical Neuroimaging

The auditory system includes 2 parallel functional pathways—one for treating sounds' identities and another for their spatial attributes (so-called "what” and "where” pathways). We examined the spatiotemporal mechanisms along auditory "what” and "where” pathways and whether they are automatically engaged in differentially processing spatial and pitch information of identical stimuli. Electrical neuroimaging of auditory evoked potentials (i.e., statistical analyses of waveforms, field strength, topographies, and source estimations) was applied to a passive "oddball” paradigm comprising 2 varieties of blocks of trials. On "what” blocks, band-pass-filtered noises varied in pitch, independently of perceived location. On "where” blocks, the identical stimuli varied in perceived location independently of pitch. Beginning 100 ms poststimulus, the electric field topography significantly differed between conditions, indicative of the automatic recruitment of distinct intracranial generators. A distributed linear inverse solution and statistical analysis thereof revealed activations within superior temporal cortex and prefrontal cortex bilaterally that were common for both conditions, as well as regions within the right temporoparietal cortices that were selective for the "where” condition. These findings support models of automatic and intrinsic parallel processing of auditory information, such that segregated processing of spatial and pitch features may be an organizing principle of auditory functio

A spatial covariance (123)I-5IA-85380 SPECT study of α4β2 nicotinic receptors in Alzheimer's disease

Alzheimer's disease (AD) is characterized by widespread degeneration of cholinergic neurons, particularly in the basal forebrain. However, the pattern of these deficits and relationship with known brain networks is unknown. In this study, we sought to clarify this and used 123I-5-iodo-3-[2(S)-2-azetidinylmethoxy] pyridine (1235IA-85380) single photon emission computed tomography to investigate spatial covariance of α4β2 nicotinic acetylcholine receptors in AD and healthy controls. Thirteen AD and 16 controls underwent 1235IA-85380 and regional cerebral blood flow (99mTc-exametazime) single photon emission computed tomography scanning. We applied voxel principal component (PC) analysis, generating series of principal component images representing common intercorrelated voxels across subjects. Linear regression generated specific α4β2 and regional cerebral blood flow covariance patterns that differentiated AD from controls. The α4β2 pattern showed relative decreased uptake in numerous brain regions implicating several networks including default mode, salience, and Papez hubs. Thus, as well as basal forebrain and brainstem cholinergic system dysfunction, cholinergic deficits mediated through nicotinic acetylcholine receptors could be evident within key networks in AD. These findings may be important for the pathophysiology of AD and its associated cognitive and behavioral phenotypes

Modulation of Ventral Prefrontal Cortex Functional Connections Reflects the Interplay of Cognitive Processes and Stimulus Characteristics

Emerging ideas of brain function emphasize the context-dependency of regional contributions to cognitive operations, where the function of a particular region is constrained by its pattern of functional connectivity. We used functional magnetic resonance imaging to examine how modality of input (auditory or visual) affects prefrontal cortex (PFC) functional connectivity for simple working memory tasks. The hypothesis was that PFC would show contextually dependent changes in functional connectivity in relation to the modality of input despite similar cognitive demands. Participants were presented with auditory or visual bandpass-filtered noise stimuli, and performed 2 simple short-term memory tasks. Brain activation patterns independently mapped onto modality and task demands. Analysis of right ventral PFC functional connectivity, however, suggested these activity patterns interact. One functional connectivity pattern showed task differences independent of stimulus modality and involved ventromedial and dorsolateral prefrontal and occipitoparietal cortices. A second pattern showed task differences that varied with modality, engaging superior temporal and occipital association regions. Importantly, these association regions showed nonzero functional connectivity in all conditions, rather than showing a zero connectivity in one modality and nonzero in the other. These results underscore the interactive nature of brain processing, where modality-specific and process-specific networks interact for normal cognitive operations