Jonathan Bamber

Jonathan Bamber


Research Interests

My current research interests are to do with sensory perception in different brain states; in particular I am interested in the perception of sound during different brain states. When attention is paid to a sound, it is almost guaranteed to be perceived; however, during sleep this ability is greatly reduced. I hope to further our understanding of sensory perception in different brain states through data analysis and computational modelling, using data obtained from simultaneous recordings from the rat auditory thalamus and auditory cortex.

Publications:
2015
  Brain state dependent stimulus information in the auditory thalamocortical system
Bamber, J, Sakata, S & Herrmann, JM 2015, 'Brain state dependent stimulus information in the auditory thalamocortical system' BMC Neuroscience, vol 16, no. 1, pp. P99. DOI: 10.1186/1471-2202-16-S1-P99
Activity in the absence of stimuli is ubiquitous across the thalamocortical system (TS), with patterns of spontaneous activity reflecting ongoing behavioural state. Under anaesthesia and during deep sleep the TS operates in an inactivated state (characterised by low frequency high amplitude oscillations in local field potential (LFP)) in which neurons collectively alternate between periods of local silence and high synaptic activity. During wakefulness and REM sleep, however, the TS operates in an activated state (characterised by high frequency low amplitude oscillations in LFP) in which neurons fire in a sustained desynchronised manner. Such brain states may be indicative of different modes of neural processing, but the effect of brain state on neural processing remains unclear.

Here we analyse data recorded in the auditory TS of urethane anaesthetised rats subjected to single-click acoustic stimulation over a range of intensities, presented in both the inactivated state (natural under the anaesthesia) and the activated state (induced through electrical stimulation of the basal forebrain). Evoked spike trains were identified for single units in the auditory thalamus and across depths of the primary auditory cortex. Mutual information (MI) between stimulus and response was then computed for spike probability, counts and timing.

Evoked spiking activity was observed to last around 300ms, consisting of distinct initial and secondary (rebound) activity. Analysis of responses of single units over a full 300ms window showed that spike count and timing measures gave little more MI than response probability, suggesting that stimulus intensity is primarily encoded probabilistically, at least at the level of the single unit. Moreover, whilst many single units are uninformative of stimulus intensity, the most informative thalamorecipient (TC) and infragranular (IF) single units show increased MI in the activated state. Additionally, upon temporally partitioning data according to initial or rebound activity, we see that TC units are more informative in the activated state during initial activity whereas IF units are more informative in the activated state during rebound activity, suggesting that information loss in the inactivated state may be cumulative in time as sensory signals propagate through neural circuits.
General Information
Organisations: Edinburgh Neuroscience.
Authors: Bamber, Jonathan, Sakata, Shuzo & Herrmann, J. Michael.
Number of pages: 1
Pages: P99
Publication Date: 2015
Publication Information
Category: Article
Journal: BMC Neuroscience
Volume: 16
Issue number: 1
ISSN: 1471-2202
Original Language: English
DOIs: 10.1186/1471-2202-16-S1-P99
2014
  Brain state dependency of stimulus-evoked spiking activity in the auditory thalamocortical system
Bamber, J, Sakata, S & Herrmann, M 2014, 'Brain state dependency of stimulus-evoked spiking activity in the auditory thalamocortical system' 9th FENS Forum of Neuroscience, Milan, Italy, 5/07/14 - 9/07/14, .
General Information
Organisations: Institute of Perception, Action and Behaviour .
Authors: Bamber, Jonathan, Sakata, Shuzo & Herrmann, Michael.
Publication Date: 2014
Publication Information
Category: Poster
Original Language: English
  Brain state dependency in the auditory thalamocortical system: mutual information and Bayesian decoding
Bamber, J, Sakata, S & Herrmann, M 2014, 'Brain state dependency in the auditory thalamocortical system: mutual information and Bayesian decoding' AREADNE 2014 Research in Encoding And Decoding of Neural Ensembles, Santorini, Greece, 25/06/14 - 29/06/14, .
The brain is never silent; throughout the thalamocortical system, spontaneous firing activity occurs in different patterns that reflect ongoing behavioural state. For example, during deep sleep and wakefulness, the thalamocortical system operates in the inactivated state in which neurons collectively aternate slowly between periods of high and near-zero firing activity, respectively referred to as up and down phases. During wakefulness and REM sleep, however, neuromodulatory mechanisms lead to the suppression of this slow oscillation, and neurons fire in a desynchronised manner in what is known as the activated state. Sensory evoked activity also is affected by brain state, and brain states may be the signatures of different modes of processing. Indeed, subtle and/or local changes in ongoing spontaneous are thought to be involved in attention. However the full implications of the effects of brain state on sensory processing remain unknown.
Here we investigate the brain state dependency of sensory processing in the auditory thalamocortical system of the rat, quantifying the amount of information about stimuli carried in the post-stimulus spike counts in individual neurons, and comparing between brain states.
Recordings used were taken simultaneously in medial geniculate body (MGB) and down a cortical column of the primary auditory cortex (A1), and auditory stimuli were presented in both the inactivated state (natural under the anaesthesia) and the activated state (induced through electrical stimulation of the basal forebrain). Quantification of stimulus information was performed through the use of the information theoretic measure of mutual information and a Bayesian decoding method known as maximum likelihood decoding.
Stimulus encoding strategies using spike counts were diverse even among cell-types and locations, as was the effect of brain state on these encoding strategies. However, information theoretic and decoding analysis revealed a shift in the amount of information carried in spike counts, with the least informative neurons tending to increase their information content in the
inactivated state, and the most informative neurons tending to decrease their information content in the inactivated state. Considering a range of window sizes and locations after stimulus presentation, a shift is also observed in the timing of when neurons were most informative.
Summarising, the quantification of stimulus information carried in spike counts allows for the brain state dependency of sensory processing to be seen at this earliest stage of cortical sensory processing, with changes observed in both the amount and timing of information conveyed.
General Information
Organisations: Institute of Perception, Action and Behaviour .
Authors: Bamber, Jonathan, Sakata, Shuzo & Herrmann, Michael.
Publication Date: 2014
Publication Information
Category: Poster
Original Language: English
  Brain state dependency of information conveyed by sensory evoked spikes in the auditory thalamocortical system
Bamber, J, Sakata, S & Herrmann, M 2014, 'Brain state dependency of information conveyed by sensory evoked spikes in the auditory thalamocortical system' Neuroscience Day 2014, Edinburgh, United Kingdom, 12/03/14 - 12/03/14, .
The mammalian thalamocortical system is always active, with ongoing spontaneous activity that differs between behavioural states. For example, the inactivated state (characterised by synchronised slow oscillations in neural firing) is associated with deep sleep, anaesthesia, and loss of consciousness, whereas the activated state (characterised by desynchronised spontaneous activity) is associated with wakefulness and paradoxical sleep. Any sensory-evoked signal must interact with ongoing local dynamics and sensory information may be processed differently in these brain states.

Here we analyse the brain state dependency of stimulus-evoked spiking activity of neurons in the rat auditory thalamus and in multiple layers of the primary auditory cortex. Stimuli were presented in both the activated and inactivated states, and spiking activity compared between cell types, cortical depths and brain states. In both states, encoding strategies are heterogeneous across cell types and locations, as is the effect of brain state on these strategies. However, information theoretic measures and a Bayesian decoding technique reveal a shift in information conveyed by neurons across all recording areas: the most informative neurons tend to be less informative in the inactivated state, whereas the least informative neurons tend to be more informative in the inactivated state. Additionally, the post-stimulus time window in which neurons are most informative shifts between brain states and varies with cell location.

In conclusion, brain state dependency of stimulus-evoked activity is evident at this early stage of cortical sensory processing, where brain state is associated with differences in the amount and timing of information conveyed through spikes.
General Information
Organisations: Institute of Perception, Action and Behaviour .
Authors: Bamber, Jonathan, Sakata, Shuzo & Herrmann, Michael.
Publication Date: 2014
Publication Information
Category: Poster
Original Language: English

Projects:
State-Dependency of Activity in Thalamocortical Circuits (PhD)