Cortical Auditory Adaptation in the Awake Rat and the Role of Potassium Currents

Responses to sound in the auditory cortex are influenced by the preceding history of firing. We studied the time course of auditory adaptation in primary auditory cortex (A1) from awake, freely moving rats. Two identical stimuli were delivered with different intervals ranging from 50 ms to 8 s. Single neuron recordings in the awake animal revealed that the response to a sound is influenced by sounds delivered even several seconds earlier, the second one usually yielding a weaker response. To understand the role of neuronal intrinsic properties in this phenomenon, we obtained intracellular recordings from rat A1 neurons in vitro and mimicked the same protocols of adaptation carried out in awake animals by means of depolarizing pulses of identical duration and intervals. The intensity of the pulses was adjusted such that the first pulse would evoke a similar number of spikes as its equivalent in vivo. A1 neurons in vitro adapted with a similar time course but less than in awake animals. At least two potassium currents participated in the in vitro adaptation: a Na +-dependent K + current and an apamin-sensitive K + current. Our results suggest that potassium currents underlie at least part of cortical auditory adaptation during the awake state.Fil: Abolafia, Juan M.. INSTITUTO DE INVESTIGACIONES BIOMEDICAS AUGUST PI I SUNYER (IDIBAPS);Fil: Vergara, Ramiro Oscar. INSTITUTO DE INVESTIGACIONES BIOMEDICAS AUGUST PI I SUNYER (IDIBAPS); . Consejo Superior de Investigaciones Científicas. Instituto de Neurociencia de Alicante; España. Universidad Nacional de Quilmes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Arnold, M. M.. Consejo Superior de Investigaciones Científicas. Instituto de Neurociencia de Alicante; España. INSTITUTO DE INVESTIGACIONES BIOMEDICAS AUGUST PI I SUNYER (IDIBAPS);Fil: Reig, R.. INSTITUTO DE INVESTIGACIONES BIOMEDICAS AUGUST PI I SUNYER (IDIBAPS);Fil: Sanchez Vives, M. V.. INSTITUTO DE INVESTIGACIONES BIOMEDICAS AUGUST PI I SUNYER (IDIBAPS)

Slow Modulation of Ongoing Discharge in the Auditory Cortex during an Interval-Discrimination Task

In this study, we recorded single unit activity from rat auditory cortex while the animals performed an interval-discrimination task. The animals had to decide whether two auditory stimuli were separated by either 150 or 300 ms, and go to the left or right nose poke accordingly. Spontaneous firing in between auditory responses was compared in the attentive versus non-attentive brain states. We describe the firing rate modulation detected during intervals while there was no auditory stimulation. Nearly 18% of neurons (n = 14) showed a prominent neuronal discharge during the interstimulus interval, in the form of an upward or downward ramp towards the second auditory stimulus. These patterns of spontaneous activity were often modulated in the attentive versus passive trials. Modulation of the spontaneous firing rate during the task was observed not only between auditory stimuli, but also in the interval preceding the stimulus. These slow modulatory components could be locally generated or the result of a top-down influence originated in higher associative association areas. Such a neuronal discharge may be related to the computation of the interval time and contribute to the perception of the auditory stimulus

Insurgent capitalism: Island, bricolage and the re-making of finance

Drawing on recent discussions of the material cultures of markets and of financial innovation as bricolage, this paper explores the development of Island, a new share-trading venue set up in 1995. We examine Island's roots in a very specific conflict in the US financial markets and in the information libertarianism of 'hacker culture', and examine the material bricolage involved in Island's construction. The paper also outlines the processes that led to a dramatic 'Latourian' change of scale: Island was originally a 'micro' development on the fringes of US markets, but within little more than a decade key features of Island became close to compulsory, as the nature of North American and Western European share trading changed utterly

Coding strategies in number space: Memory requirements influence spatial-numerical associations

The tendency to respond faster with the left hand to relatively small numbers and faster with the right hand to relatively large numbers (spatial numerical association of response codes, SNARC effect) has been interpreted as an automatic association of spatial and numerical information. We investigated in two experiments the impact of task-irrelevant memory representations on this effect. Participants memorized three Arabic digits describing a left-to-right ascending number sequence (e.g., 3-4-5), a descending sequence (e.g., 5-4-3), or a disordered sequence (e.g., 5-3-4) and indicated afterwards the parity status of a centrally presented digit (i.e., 1, 2, 8, or 9) with a left/right keypress response. As indicated by the reaction times, the SNARC effect in the parity task was mediated by the coding requirements of the memory tasks. That is, a SNARC effect was only present after memorizing ascending or disordered number sequences but disappeared after processing descending sequences. Interestingly, the effects of the second task were only present if all sequences within one experimental block had the same type of order. Taken together, our findings are inconsistent with the idea that spatial-numerical associations are the result of an automatic and obligatory cognitive process but do suggest that coding strategies might be responsible for the cognitive link between numbers and space. © 2007 The Experimental Psychology Society.Peer Reviewe

Coding strategies in number space:Memory requirements influence spatial-numerical associations

The tendency to respond faster with the left hand to relatively small numbers and faster with the right hand to relatively large numbers (spatial numerical association of response codes, SNARC effect) has been interpreted as an automatic association of spatial and numerical information. We investigated in two experiments the impact of task-irrelevant memory representations on this effect. Participants memorized three Arabic digits describing a left-to-right ascending number sequence (e.g., 3-4-5), a descending sequence (e.g., 5-4-3), or a disordered sequence (e.g., 5-3-4) and indicated afterwards the parity status of a centrally presented digit (i.e., 1, 2, 8, or 9) with a left/right keypress response. As indicated by the reaction times, the SNARC effect in the parity task was mediated by the coding requirements of the memory tasks. That is, a SNARC effect was only present after memorizing ascending or disordered number sequences but disappeared after processing descending sequences. Interestingly, the effects of the second task were only present if all sequences within one experimental block had the same type of order. Taken together, our findings are inconsistent with the idea that spatial-numerical associations are the result of an automatic and obligatory cognitive process but do suggest that coding strategies might be responsible for the cognitive link between numbers and space

Cortical auditory adaptation in the awake rat and the role of potassium currents

Responses to sound in the auditory cortex are influenced by the preceding history of firing. We studied the time course of auditory adaptation in primary auditory cortex (A1) from awake, freely moving rats. Two identical stimuli were delivered with different intervals ranging from 50 ms to 8 s. Single neuron recordings in the awake animal revealed that the response to a sound is influenced by sounds delivered even several seconds earlier, the second one usually yielding a weaker response. To understand the role of neuronal intrinsic properties in this phenomenon, we obtained intracellular recordings from rat A1 neurons in vitro and mimicked the same protocols of adaptation carried out in awake animals by means of depolarizing pulses of identical duration and intervals. The intensity of the pulses was adjusted such that the first pulse would evoke a similar number of spikes as its equivalent in vivo. A1 neurons in vitro adapted with a similar time course but less than in awake animals. At least two potassium currents participated in the in vitro adaptation: a Na +-dependent K+ current and an apamin-sensitive K + current. Our results suggest that potassium currents underlie at least part of cortical auditory adaptation during the awake state. © The Author 2010. Published by Oxford University Press. All rights reserved.Spanish Ministry of Science and Innovation (Spain) (BFU2008-01371/BFI); PRESENCCIA project (EU-FP6-27731).Peer Reviewe

Lateral orbitofrontal cortex anticipates choices and integrates prior with current information

Adaptive behavior requires integrating prior with current information to anticipate upcoming events. Brain structures related to this computation should bring relevant signals from the recent past into the present. Here we report that rats can integrate the most recent prior information with sensory information, thereby improving behavior on a perceptual decision-making task with outcome-dependent past trial history. We find that anticipatory signals in the orbitofrontal cortex about upcoming choice increase over time and are even present before stimulus onset. These neuronal signals also represent the stimulus and relevant second-order combinations of past state variables. The encoding of choice, stimulus and second-order past state variables resides, up to movement onset, in overlapping populations. The neuronal representation of choice before stimulus onset and its build-up once the stimulus is presented suggest that orbitofrontal cortex plays a role in transforming immediate prior and stimulus information into choices using a compact state-space representation.R.N. is supported by a FI-AGAUR scholarship from the Government of Catalonia. R.M.-B. is supported by PSI2013-44811-P and FLAGERA-PCIN-2015-162-C02-02 from MINECO (Spain). M.V.S.-V. is supported by BFU2014-52467-R and SlowDyn FLAGERA-PCIN-2015-162-C02-01 from MINECO. This work was supported by CERCA Programme / Generalitat de Catalunya. We thank Julio Martinez-Trujillo for comments on the manuscript