Biology subjects

Bell, A. H.

Publications and source records attributed to Bell, A. H..

5 recordsLinked to original sources

bioRxiv2024

Effect of copper mill waste material on benthic invertebrates and zooplankton diversity and abundance in Lake Superior beaches

From 1900 to 1932 a copper (Cu) mill operated near Gay, Michigan, along the eastern shore of the Keweenaw Peninsula (Lake Superior, Michigan) and discharged waste material (stamp sands [SS]) to a nearby beach. These SS escaped containment structures and have been redeposited by wave action along the beaches in northern Grand Traverse Bay and onto Buffalo Reef, an important spawning area for native fish. Newly hatched fish move into nearby beach habitats where they grow during their first summer. Juvenile fish initially consume zooplankton before switching to benthic invertebrates once they are large enough. SS contain metals (especially Cu) that are toxic to many invertebrate taxa, and studies have observed few benthic taxa in areas covered by SS. We sampled the invertebrate community from four Lake Whitefish nursery areas: one near Buffalo Reef with high SS, one south of the Traverse River with moderate SS, one in nearby Little Traverse Bay with little SS, and a beach [~]58 km away with no SS (Big Bay). We also resampled the benthos at sites that had been sampled as part of an earlier Grand Traverse Bay study. Buffalo Reef (high SS) had fewer benthic taxa, and less density of several taxa than Little Traverse Bay (little SS), especially benthic copepods. All beaches had comparable zooplankton diversity, but the abundance was [~]2 orders of magnitude lower at Buffalo Reef (high SS) than other beaches. Cu and several other metals were elevated at beaches with more SS. We found support for associations between benthic density and diversity with depth (positive effect) and Cu concentration (negative effect). Cu concentration was a better predictor of declines in benthic invertebrate abundance and diversity than SS. We also observed that the relationship between Cu concentration and SS was non-linear, and highly variable. For example, 149 mg Cu/kg dry weight sediment is a consensus toxicity threshold used in the literature, but the prediction interval around that concentration from our model is 26-851 mg Cu/kg dry weight. A better predictive model of this relationship would be beneficial to develop to understand what level of SS reduction would prevent Cu impacts on invertebrates.

ecology↗

bioRxiv2020

Perceived ambiguity of social interactions increases coupling between frontal and temporal nodes of the social brain

Social behaviour is coordinated by a network of brain regions, including those involved in the perception of social stimuli and those involved in complex functions like inferring perceptual and mental states and controlling social interactions. The properties and function of many of these regions in isolation is relatively well understood but little is known about how these regions interact whilst processing dynamic social interactions. To investigate whether social network connectivity is modulated by social context we collected fMRI data from monkeys viewing "affiliative", "aggressive", or "ambiguous" social interactions. We show activation relating to the perception of social interactions along both banks of the superior temporal sulcus, parietal, medial and lateral PFC and caudate nucleus. Within this network we demonstrate that fronto-temporal connectivity are significantly modulated by social context. Crucially, we link the observation of specific behaviours to changes in connectivity within our network. Viewing aggressive or affiliative behaviour was associated with a limited increase in temporo-temporal and premotor-temporal connectivity respectively. By contrast, viewing ambiguous interactions was associated with a pronounced increase in cingulate-cingulate, temporo-temporal, and cingulate-temporal connectivity. We hypothesise that this widespread network synchronisation occurs when cingulate and temporal areas coordinate their activity when more difficult social inferences are made.

neuroscience↗

bioRxiv2019

Frontopolar cortex is a mediator of network modularity in the primate brain

Primate frontopolar cortex (FPC), occupied by area 10, sits atop a functional hierarchy of prefrontal cortical regions yet little is known about its causal role influencing cognition and brain networks. We studied resting-state-functional-connectivity (rsfc) networks in rhesus monkeys with or without FPC; 86 cortical regions showed significant differences in inter-area rsfc measures in lesioned animals versus controls. K-means clustering showed these regions were organized into two distinct networks in lesioned animals, whereas the same areas clustered into four networks in control animals. These networks extended within and beyond prefrontal cortex. These results suggest that FPC is involved in mediating cortical networks in the primate brain, both within and beyond prefrontal cortex. Even after 40 months only partial recovery of lesion-induced reduced modularity had occurred. We therefore suggest that FPC might help implement long-standing diverse neural network dynamics.

neuroscience↗

bioRxiv2018

Intact extrastriate visual network without primary visual cortex in a Rhesus macaque with naturally occurring Blindsight

Lesions of primate primary visual cortex (V1) lead to loss of conscious visual perception, and are often devastating to those affected. Understanding the neural consequences of such damage may aid the development of rehabilitation methods. In this rare case of a Rhesus macaque (monkey S), likely born without V1, we investigated the brain structures underlying residual visual abilities using multimodal magnetic resonance imaging. In-group behaviour was unremarkable. Compared to controls, visual structures outside of monkey Ss lesion appeared normal. Visual stimulation under anaesthesia with checkerboards activated lateral geniculate nucleus of monkey S, but not the pulvinar, while full-field moving dots activated the pulvinar. Functional connectivity analysis revealed a network of bilateral dorsal visual areas temporally correlated with V5/MT, consistent across lesion and control animals. Overall, we found an intact network of visual cortical areas even without V1, but little evidence for strengthened subcortical input to V5/MT supporting residual visual function.

neuroscience↗

bioRxiv2017

Functional reorganisation and recovery following cortical lesions: A study in macaque monkeys

Damage following traumatic brain injury or stroke can often extend beyond the boundaries of the initial insult and can lead to maladaptive cortical reorganisation. On the other hand, beneficial cortical reorganisation leading to recovery of function can also occur. Here, we used resting state FMRI (rsFMRI) to examine how functional connectivity in the macaque brain changed across time in response to lesions to the prefrontal cortex, and how this reorganisation correlated with changes in behaviour. Two monkeys were trained to perform location-based and object-based delayed match-to-sample tasks. We also collected rsFMRI data under general anaesthesia at two pre-lesion time-points, separated by 3-4 weeks. After two cycles of testing and scanning, the animals received a principal sulcus lesion followed by an additional 4 cycles of testing and scanning. Later, the same animals received a second lesion to the opposite hemisphere and additional cycles of testing and scanning.\n\nBoth animals showed a marked behavioural impairment following the first lesion, which was associated with a decrease in functional connectivity, predominantly within frontal-frontal networks in both hemispheres. Approximately 8 weeks following the lesion, performance improved, as did functional connectivity within these networks. Following the second lesion, functional connectivity again decreased and this was associated with a marginal behavioural deficit that did not recover.\n\nOur data show that behavioural impairments reflect not just the removal of the lesioned area, but also disturbance to an extensive cortical network. This network can recover by restoring and/or strengthening pre-existing connections, leading to improvement in behaviour.

neuroscience↗