GABAergic excitation in the basolateral amygdala

GABA-containing interneurons are a diverse population of cells whose primary mode of action in the mature nervous system is inhibition of postsynaptic target neurons. Using paired recordings from parvalbumin-positive interneurons in the basolateral amygdala, we show that, in a subpopulation of interneurons, single action potentials in one interneuron evoke in the postsynaptic interneuron a monosynaptic inhibitory synaptic current, followed by a disynaptic excitatory glutamatergic synaptic current. Interneuron-evoked glutamatergic events were blocked by antagonists of either AMPA/kainate or GABA(A) receptors, and could be seen concurrently in both presynaptic and postsynaptic interneurons. These results show that single action potentials in a GABAergic interneuron can drive glutamatergic principal neurons to threshold, resulting in both feedforward and feedback excitation. In interneuron pairs that both receive glutamatergic inputs after an interneuron spike, electrical coupling and bidirectional GABAergic connections occur with a higher probability relative to other interneuron pairs. We propose that this form of GABAergic excitation provides a means for the reliable and specific recruitment of homogeneous interneuron networks in the basal amygdala

The Enigmatic Function of Chandelier Cells

Chandelier (or axo-axonic) cells are one of the most distinctive GABAergic interneurons in the brain. Their exquisite target specificity for the axon initial segment of pyramidal neurons, together with their GABAergic nature, long suggested the possibility that they provide the ultimate inhibitory control of pyramidal neuron output. Recent findings indicate that their function may be more complicated, and perhaps more interesting, than initially believed. Here we review these recent developments and their implications. We focus in particular on whether chandelier cells may provide a depolarizing, excitatory effect on pyramidal neuron output, in addition to a powerful inhibition

Depolarizing Effect of Neocortical Chandelier Neurons

Chandelier (or axo-axonic) cells are one of the most distinctive types of GABAergic interneurons in the cortex. Although they have traditionally been considered inhibitory neurons, data from rat and human neocortical preparations suggest that chandelier cells have a depolarizing effect on pyramidal neurons at resting membrane potential, and could even activate synaptic chains of neurons. At the same time, recent results from rat hippocampal chandeliers indicate a predominantly inhibitory effect on their postsynaptic targets. To better understand the function of chandelier neurons, we generated Nkx2.1Cre MADM mice, a strain of genetically engineered animals that, by expressing GFP in a subset of neocortical interneurons, enable the identification and targeting of chandelier cells in living brain slices. Using these mice, we characterized the basic electrophysiological properties of a homogeneous population of chandelier neurons from upper layers of somatosensory cortical slices. These chandelier cells have characteristic axon cartridges and stereotypical electrophysiological features, distinguishable from basket cells. To investigate the effect of chandelier cells on target neurons, we performed paired recordings from chandeliers and postsynaptic pyramidal cells. In both perforated patch and cell-attached configurations, chandelier PSPs have in every case a reversal potential that is depolarized from rest. Our results support the idea that chandelier cells depolarize pyramidal neurons and could potentially have an excitatory effect on the network at rest

SLM Microscopy: Scanless Two-Photon Imaging and Photostimulation with Spatial Light Modulators

Laser microscopy has generally poor temporal resolution, caused by the serial scanning of each pixel. This is a significant problem for imaging or optically manipulating neural circuits, since neuronal activity is fast. To help surmount this limitation, we have developed a “scanless” microscope that does not contain mechanically moving parts. This microscope uses a diffractive spatial light modulator (SLM) to shape an incoming two-photon laser beam into any arbitrary light pattern. This allows the simultaneous imaging or photostimulation of different regions of a sample with three-dimensional precision. To demonstrate the usefulness of this microscope, we perform two-photon uncaging of glutamate to activate dendritic spines and cortical neurons in brain slices. We also use it to carry out fast (60 Hz) two-photon calcium imaging of action potentials in neuronal populations. Thus, SLM microscopy appears to be a powerful tool for imaging and optically manipulating neurons and neuronal circuits. Moreover, the use of SLMs expands the flexibility of laser microscopy, as it can substitute traditional simple fixed lenses with any calculated lens function

Texas STATEMAP Program Summary, FY19 (2019–2020)

Five geologic maps have been completed at a 1:24,000 scale in four project areas with support from STATEMAP and the Bureau of Economic Geology's State of Texas Advanced Resource Recovery program (STARR). Three of these maps were on the Texas Coastal Plain, including one (the Lake Stephenson quadrangle) on the upper Texas Coastal Plain in the Galveston Bay area and two (the Bloomington and Olivia quadrangles) on the middle Texas Coastal Plain in the Matagorda Bay area. These maps continue efforts to: 1. Better understand the evolution of the coastal plain in response to sea-level changes associated with numerous Quaternary glacial and interglacial cycles. 2. Develop more effective methods to map low-relief coastal deposits using high-resolution topographic maps produced from airborne lidar data and near-surface geophysical methods. High-resolution topography and geophysical methods both aid in the identification of stratal units and their distribution in areas where exposures are poor or nonexistent. Mineral-resource mapping produced one map (the Katemcy quadrangle) to extend recent mapping of an industrial sand resource area in central Texas. This map facilitates the development of mineral resources of the state, emphasizing those that will help meet the demand for industrial sand for hydraulic fracturing and construction. The detailed map can be used to evaluate and explore the mineral-resource potential of the area. Mapping in the central Texas urban growth corridor northeast of Austin produced one map (the Taylor quadrangle) that extends previous mapping in this critical urban growth and transportation corridor. This map addresses the ongoing need for planning and managing groundwater, surface water, land use, and construction projects where rapid population growth and suburban development have caused an increased demand for water and earth resources.Bureau of Economic Geolog

A Vehicle for Research: Using Street Sweepers to Explore the Landscape of Environmental Community Action

Researchers are developing mobile sensing platforms to facilitate public awareness of environmental conditions. However, turning such awareness into practical community action and political change requires more than just collecting and presenting data. To inform research on mobile environmental sensing, we conducted design fieldwork with government, private, and public interest stakeholders. In parallel, we built an environmental air quality sensing system and deployed it on street sweeping vehicles in a major U.S. city; this served as a "research vehicle" by grounding our interviews and affording us status as environmental action researchers. In this paper, we present a qualitative analysis of the landscape of environmental action, focusing on insights that will help researchers frame meaningful technological interventions.Comment: 10 page

Two-Photon Microscopy with Diffractive Optical Elements and Spatial Light Modulators

Two-photon microscopy is often performed at slow frame rates due to the need to serially scan all points in a field of view with a single laser beam. To overcome this problem, we have developed two optical methods that split and multiplex a laser beam across the sample. In the first method a diffractive optical element (DOE) generates a fixed number of beamlets that are scanned in parallel resulting in a corresponding increase in speed or in signal-to-noise ratio in time-lapse measurements. The second method uses a computer-controlled spatial light modulator (SLM) to generate any arbitrary spatio-temporal light pattern. With an SLM one can image or photostimulate any predefined region of the image such as neurons or dendritic spines. In addition, SLMs can be used to mimic a large number of optical transfer functions including light path corrections as adaptive optics

The Lantern Vol. 61, No. 1, December 1993

• In Order to Succeed • Essay • Power of Human Self-Interest: Man vs. Car • In Setterich • Wandering Wanda • Maybe Kitchens • Saltiness • Homecoming • Perfect • Sincerely, Jen • A Midterm and a Paper • Prophet Junkie • Soundless Memo • After Ireland, Part 1https://digitalcommons.ursinus.edu/lantern/1142/thumbnail.jp

Of Mice and Men, and Chandeliers

How does the human neocortex reliably propagate information through neural circuits? One mechanism appears to involve relying on strong connections from pyramidal neurons to interneurons and a depolarizing action of cortical chandelier cells

Biology and genome of a newly discovered sibling species of Caenorhabditis elegans

A ‘sibling’ species of the model organism Caenorhabditis elegans has long been sought for use in comparative analyses that would enable deep evolutionary interpretations of biological phenomena. Here, we describe the first sibling species of C. elegans, C. inopinata n. sp., isolated from fig syconia in Okinawa, Japan. We investigate the morphology, developmental processes and behaviour of C. inopinata, which differ significantly from those of C. elegans. The 123-Mb C. inopinata genome was sequenced and assembled into six nuclear chromosomes, allowing delineation of Caenorhabditis genome evolution and revealing unique characteristics, such as highly expanded transposable elements that might have contributed to the genome evolution of C. inopinata. In addition, C. inopinata exhibits massive gene losses in chemoreceptor gene families, which could be correlated with its limited habitat area. We have developed genetic and molecular techniques for C. inopinata; thus C. inopinata provides an exciting new platform for comparative evolutionary studies