Segregating Cities, Separating Environments: A Look At The Relationship Between Redlining And Polluting Facilities In Philadelphia

This thesis explores the relationship between federal redlining policy and the siting of air polluting facilities, using a dual approach of geospatial analysis and historiography on Philadelphia as a case study. Geographic Information System (GIS) tools are applied to Environmental Protection Agency (EPA) data on air polluting facilities and the Home Owners’ Loan Corporation (HOLC) Residential Security Maps. This analysis is used to determine the number of facilities within redlined neighborhoods and their patterns of density. Findings suggest that higher concentrations of polluting facilities are present in those neighborhoods ranked lowest by the HOLC, while neighborhoods ranked highest show remarkably fewer facilities. Historiography is then used to assess the processes of industrial and residential development over time, and determine connections between redlining and shifting land use patterns in Philadelphia. Overall, historiography reveals that redlining reaffirmed pre-existing socio-spatial patterns, and served to advance processes of disinvestment in redlined neighborhoods and the concentration of polluting facilities in these regions. The work of this paper indicates that both formal and informal practices around redlining contributed to stigmatization of lowest ranked neighborhoods, and suggests a proximate relationship between marginalized communities and sources of pollution

Delta/theta-rhythmically interleaved gamma and beta oscillations in striatum: modeling and data analysis

Striatal oscillatory activity associated with movement, reward, and decision-making is observed in several interacting frequency bands. Rodent striatal local field potential recordings show dopamine- and reward-dependent transitions between a 'spontaneous' state involving beta (15-30 Hz) and low gamma (40-60 Hz) and a 'dopaminergic' state involving theta (4-8 Hz) and high gamma (60-100 Hz) activity. The mechanisms underlying these rhythmic dynamics and their functional consequences are not well understood. In this thesis, I construct a biophysical model of striatal microcircuits that comprehensively describes the generation and interaction of these rhythms as well as their modulation by dopamine and rhythmic inputs, and test its predictions using human electroencephalography (EEG) data. Chapter 1 describes the striatal model and its dopaminergic modulation. Building on previous work suggesting striatal projection neuron (SPN) networks can generate beta oscillations, I construct a model network of striatal fast-spiking interneurons (FSIs) capable of generating delta/theta (2-6 Hz) and gamma rhythms. This FSI network produces low gamma oscillations under low (simulated) dopaminergic tone, and high gamma activity nested within a delta/theta oscillation under high dopaminergic tone. In a combined model under high dopaminergic tone SPN network beta oscillations are interrupted by delta/theta-periodic bursts of gamma-frequency FSI inhibition. This high dopamine-induced periodic inhibition may enable switching between beta-rhythmic SPN cell assemblies representing motor programs, suggesting that dopamine facilitates movement in part by allowing for rapid, periodic changes in motor program execution. Chapter 2 describes the model's response to square-wave periodic cortical inputs. Comparing models with and without FSIs reveals that the FSI network: (i) prevents the SPN network's generation of phase-locked beta oscillations in response to beta's harmonic frequencies, ensuring fidelity of transmission of cortical beta rhythms; and (ii) limits or entrains SPN activity in response to certain gamma frequency inputs. Chapter 3 describes an analysis of phase-amplitude coupling at cortical electrodes in human EEG data during a reward task. The alternating rhythms predicted by the model appear in response to positive feedback. While the origins of these rhythms remain unclear, if they represent striatal signals, they provide a direct link between human behavior and striatal cellular function

A biophysical model of striatal microcircuits suggests gamma and beta oscillations interleaved at delta/theta frequencies mediate periodicity in motor control

Striatal oscillatory activity is associated with movement, reward, and decision-making, and observed in several interacting frequency bands. Local field potential recordings in rodent striatum show dopamine- and reward-dependent transitions between two states: a "spontaneous" state involving β (∼15-30 Hz) and low γ (∼40-60 Hz), and a state involving θ (∼4-8 Hz) and high γ (∼60-100 Hz) in response to dopaminergic agonism and reward. The mechanisms underlying these rhythmic dynamics, their interactions, and their functional consequences are not well understood. In this paper, we propose a biophysical model of striatal microcircuits that comprehensively describes the generation and interaction of these rhythms, as well as their modulation by dopamine. Building on previous modeling and experimental work suggesting that striatal projection neurons (SPNs) are capable of generating β oscillations, we show that networks of striatal fast-spiking interneurons (FSIs) are capable of generating δ/θ (ie, 2 to 6 Hz) and γ rhythms. Under simulated low dopaminergic tone our model FSI network produces low γ band oscillations, while under high dopaminergic tone the FSI network produces high γ band activity nested within a δ/θ oscillation. SPN networks produce β rhythms in both conditions, but under high dopaminergic tone, this β oscillation is interrupted by δ/θ-periodic bursts of γ-frequency FSI inhibition. Thus, in the high dopamine state, packets of FSI γ and SPN β alternate at a δ/θ timescale. In addition to a mechanistic explanation for previously observed rhythmic interactions and transitions, our model suggests a hypothesis as to how the relationship between dopamine and rhythmicity impacts motor function. We hypothesize that high dopamine-induced periodic FSI γ-rhythmic inhibition enables switching between β-rhythmic SPN cell assemblies representing the currently active motor program, and thus that dopamine facilitates movement in part by allowing for rapid, periodic shifts in motor program execution.R01 MH114877 - NIMH NIH HHSPublished versio

Noninvasive neurostimulation of left ventral motor cortex enhances sensorimotor adaptation in speech production

Sensorimotor adaptation¬—enduring changes to motor commands due to sensory feedback—allows speakers to match their articulations to intended speech acoustics. How the brain integrates auditory feedback to modify speech motor commands and what limits the degree of these modifications remain unknown. Here, we investigated the role of speech motor cortex in modifying stored speech motor plans. In a within-subjects design, participants underwent separate sessions of sham and anodal transcranial direct current stimulation (tDCS) over speech motor cortex while speaking and receiving altered auditory feedback of the first formant. Anodal tDCS increased the rate of sensorimotor adaptation for feedback perturbation. Computational modeling of our results using the Directions Into Velocities of Articulators (DIVA) framework of speech production suggested that tDCS primarily affected behavior by increasing the feedforward learning rate. This study demonstrates how focal noninvasive neurostimulation can enhance the integration of auditory feedback into speech motor plans.This research was supported by NIDCD of the NIH under award numbers R03DC014045 to TP, and R01DC002852 to FG. TLS was supported by T90DA032484. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Healt

A biophysical model of striatal microcircuits suggests delta/theta - rhythmically interleaved gamma and beta oscillations mediate periodicity in motor control

First author draf