Solomon Lab

NETWORK CHANGES IN MOUSE MODELS OF DEMENTIA

There is great need for functional markers of neurodegenerative diseases, particularly if they can be provided by low-cost measurements of brain activity such as the electroencephalogram (EEG). Indeed, there are clear correlates of Alzheimer's Disease in the EEG signal. However, clinical measures of electrical brain activity usually characterise the amplitude of brain oscillations at different frequencies. A potentially more sensitive measure is the functional coupling between brain areas, which can be indexed by the co-variation or coherence of oscillations between areas.

We are therefore currently using electrophysiological tools to ask whether long-distance connections between mouse brain areas, which are sparser than local connections within brain areas, may be particularly sensitive to the disruption of intracellular machinery during neurodegeneration. In parallel we are testing the hypothesis that sensory (visual) responses may be good early indicators of the presence of dysfunction, and more broadly that visual processing (probably the most understood of brain processes) can provide a framework for understanding how neurodegeneration affects in formation processing in the brain.

This work is currently and previously supported by MRC Project Grants including one in collaboration with Lilly Pharmaceuticals.

Selected publications

A Papanikolaou, FR Rodrigues, J Holeniewska, K Phillips, AB Saleem, SG Solomon (2022). Communications Biology. Plasticity in visual cortex is disrupted in a mouse model of tauopathy.

FR Rodrigues, A Papanikolaou, J Holeniewska, K Phillips, AB Saleem, SG Solomon (2022). iScience. Altered low frequency brain rhythms precede changes in gamma power during tauopathy.

BRAIN PATHWAYS FOR INSTINCTIVE BEHAVIOURS

Prey species including mice express rapid avoidance behaviours that appear to be innately triggered by appropriate sensory stimuli. We have been exploring these behaviours, and the neural mechanisms that may underlie them. In addition we are interested in using these unconditioned behaviours to understand basic aspects of visual processing (in healthy animals and in animals with retinal or central disease) as well as higher order cognitive behaviours such as choice, navigation and attention. Our hope is that these simple behaviours may be supported by tractable machinery, that allow deep insight into ancient brain circuits as well as more recently evolved circuits that may have built on them.

This work was supported by a BBSRC Project Grant to Sam Solomon, Kate Jeffery and Aman Saleem "Brain pathways for visually- guided defence behaviours"

In the news: for a comment on De Franceschi and Solomon (2018) see Triplett (2018) 'Neurons in the superior colliculus wake up to see things differently'.

Selected publications

SG Solomon, H Janbon, A Bimson, T Wheatcroft (2023). Royal Society Open Science. Visual spatial location influences selection of instinctive behaviours in mouse.

T Wheatcroft, AB Saleem, SG Solomon (2022). Frontiers in Neural Circuits. Functional organisation of the mouse superior colliculus.

G Lopes, K Farrell, EAB Horrocks, C-Y Lee, MM Morimoto, T Muzzu, A Papanikolaou, FR Rodrigues, T Wheatcroft, S Zucca, SG Solomon, AB Saleem (2021). eLife. Creating and controlling visual environments using BonVision.

G De Franceschi and SG Solomon (2018) Journal of Physiology. Visual response properties of neurons in the superficial layers of superior colliculus of awake mouse.

G De Franceschi et al. (2016) Current Biology. Vision guides selection of freeze of flight defence strategies in mice.

GAIN CONTROLS IN EARLY VISUAL PATHWAYS

The responses of neurons in the visual pathways of the brain depends on both the spatial and temporal context in which a stimulus (eg. an edge) is presented. The mechanisms that provide this context sensitivity are often called “gain controls”. They are thought to be ubiquitous in visual and other sensory systems, and may be analagous to other brain mechanisms that help learning and decision making. Abnormal gain controls may underly several important brain disorders, and also influence the capacity of clinical tests to detect changes in visual sensitivity that accompany, for example, macular degeneration. Despite their ubiquity, we do not know whether these gain controls are expressed all of the parallel visual pathways, or whether their impact on processing is the same in each case. In this work, we are investigating the prevalence and signatures of gain controls in the visual thalamus and mid-brain. We are also developing fMRI of visual pathways in mouse to make systematic measurements across these parallel pathways.

Aspects of this work were supported by a Career Integration Grant from the Marie Curie scheme of the European Commission "PVPITM", and by a Wellcome Trust Strategic Infrastructure Award, and an International Collaboration Award from Research to Prevent Blindness and Stavros Niarchos Foundation with Adam Kohn.

Selected publications

JM Bosten, R Coen-Cagli, A Franklin, SG Solomon, MA Webster (2022). Vision research. Calibrating vision: Concepts and questions

M Fritsche, SG Solomon, F P. de Lange (2022) Journal of Neuroscience. Brief stimuli cast a persistent long-term trace in visual cortex.

G De Franceschi, SG Solomon (2020) eNeuro. Dynamic Contextual Modulation in Superior Colliculus of Awake Mouse

A Aschner, SG Solomon, MS Landy, DJ Heeger, A Kohn (2018) Journal of Neuroscience. Temporal contingencies determine whether adaptation strengthens or weakens normalization.

J Larsson, SG Solomon, A Kohn (2016) Cortex. fMRI adaptation revisited.

A Niranjan, IN Christie, SG Solomon, JA Wells, MF Lythgoe (2016) Neuroimage. fMRI mapping of the visual system in the mouse brain with interleaved snapshot GE-EPI

SG Solomon, A Kohn (2014) Current Biology. Moving Sensory Adaptation beyond Suppressive Effects in Single Neurons.

WHAT DOES THE CORTEX SEE?

What signals are passed form the retina to primary visual cortex? Textbooks will tell you that there are two main pathways - the "magnocellular", and "parvocellular" - and that these provide signals necessary for motion and form/colour vision respectively. We have explored the signals provided by a third pathway, the evolutionarily older "koniocellular" pathway, and find that neurons there can show remarkable properties, including selectivity to oriented edges, and capacity to be excited by inputs from either eye. Both these properties were thought to emerge in visual cortex, so their existence in the areas of the brain that provide input to cortex raises many questions about how they contribute to subsequent processing. In addition we have found that some nerve cells in the early visual pathway show shared activity - this is manifest at long time scales (slow rhythms), yoked to fluctuations in the electroencephalogram over visual cortex, and is confined to the koniocellular pathway.

This work was funded by grants from the National Health and Medical Research Council of Australia from 2006-2017, most recently by (NHMRC; 2015-17; PI Paul Martin) "Brain pathways serving conscious and sub-conscious vision"

In the news: for a comment on Solomon et al. (1999) see Vivien Casagrande (1999) "The mystery of the visual system K pathway"; for a discussion of Cheong et al. (2013), among others, see Cris Niell (2013) "Vision: more than expected in the early visual system"; for a comment on Zeater et al. (2015) see Wallace et al. (2016) "Primate thalamus: more than meets the eye".

Selected publications:

CD Eiber, A Rahman, ANJ Pietersen, N Zeater, B Dreher, SG Solomon, PR Martin (2018) Journal of Neuroscience. Receptive field properties of koniocellular on/off neurons in the lateral geniculate nucleus of marmoset monkeys

N Zeater, SK Cheong, SG Solomon, B Dreher, PR Martin (2015). Current Biology. Binocular visual responses in the primate lateral geniculate nucleus.

SK Cheong, C Tailby, SG Solomon, PR Martin (2013) Journal of Neuroscience. Cortical-like receptive fields in the lateral geniculate nucleus of marmoset monkeys.

SK Cheong , C Tailby, PR Martin, JB Levitt, SG Solomon (2011). Proceedings of the National Academy of Sciences of the USA. Slow intrinsic rhythm in the koniocellular visual pathway.

C Tailby, SG Solomon, N Dhruv, N Majaj, S Sokol, P Lennie (2007) Journal of Neuroscience. A new code for contrast early in the visual pathway

SG Solomon, AJR White, PR Martin (2002) Journal of Neuroscience. Extraclassical receptive field properties of parvocellular, magnocellular, and koniocellular cells in the primate lateral geniculate nucleus.

AJR White, SG Solomon, PR Martin (2001) Journal of Physiology. Spatial properties of koniocellular cells in the lateral geniculate nucleus of the common marmoset, Callithrix jacchus

SG Solomon, AJR White, PR Martin (1999) Journal of Physiology. Temporal sensitivity in the lateral geniculate nucleus of a New World monkey, the marmoset Callithrix jacchus.

MOTION SIGNALS IN THE CEREBRAL CORTEX

In primates including humans a small area of the cerebral cortex - area MT - is thought to hold a special role in motion vision and the control of eye movements. We have been making measurements of the motion signals carried by single nerve cells in area MT, and in populations of nerve cells there. We are particularly interested in 1) how the functional connectivity of neurons constrains the signals that they provide, and 2) how signals for surface segmentation (eg. transparency) and surface integration (eg. 'pattern motion') are carried by individual nerve cells.

This work was supported by grants from the Australian Research Council (ARC; 2016-18) "Representational geometry: predicting behaviour from brain representations" (PI Tom Carlson) & "Propagating neural waves: combined experimental and modelling study" (PI Pulin Gong)

Selected publications:

Y Liu, X Long, PR Martin, SG Solomon, P Gong (2021). Communications Biology. Lévy walk dynamics explain gamma burst patterns in primate cerebral cortex.

E Goddard, C Klein, SG Solomon, H Hogendoorn, TA Carlson (2018) Neuroimage. Interpreting the dimensions of neural feature representations revealed by dimensionality reduction.

RG Townsend, SS Solomon, SC Chen, ANJ Pietersen, PR Martin, SG Solomon, P Gong (2017). Journal of Neuroscience. Visual motion discrimination by propagating patterns in primate cerebral cortex

SS Solomon, JW Morley, SG Solomon (2017) Cerebral Cortex. Spectral signatures of feedforward and recurrent circuitry in monkey area MT.

E Goddard, SG Solomon, TA Carlson (2017) Journal of Neurophysiology. Dynamic Population Codes of Multiplexed Stimulus Features in Primate Area MT

SS Solomon, SC Chen, JW Morley, SG Solomon (2015) Cerebral Cortex. Local and global correlations between neurons in the middle temporal area of primate visual cortex.

JS McDonald, CWG Clifford, SS Solomon, SC Chen, SG Solomon (2014) Journal of Neurophysiology. Integration and segregation of multiple motion signals by neurons in area MT of primate.

Solomon SS, Tailby C, Gharaei S, Camp AJ, Bourne JA, Solomon SG (2011). Journal of Physiology, Visual motion integration in the middle temporal area of a New World monkey, the marmoset.

TEMPORAL CONTEXT

Prolonged viewing of a simple pattern leads to changes in its appearances, and of similar patterns. It has long been thought that this reflects the habituation of nerve cells in the visual parts of the cerebral cortex. We have shown that habituation is not confined to cortex, but instead first arises in the eye, and is strongest in nerve cells that are part of the "magnocellular-pathway", thought to be important in motion vision. Our observations also provide a way in which to non-invasively 'knock-out' this population of nerve-cells in normal humans and animals.

Selected publications:

M Fritsche, SG Solomon, F P. de Lange (2022). Journal of Neuroscience. Brief stimuli cast a persistent long-term trace in visual cortex.

SG Solomon, A Kohn (2014) Current Biology. Moving Sensory Adaptation beyond Suppressive Effects in Single Neurons

S Di Marco, DA Protti, SG Solomon (2013) Journal of Neurophysiology. Excitatory and inhibitory contributions to receptive fields of alpha-like retinal ganglion cells in mouse.

AJ Camp, C Tailby, SG Solomon (2009) Journal of Neuroscience. Adaptable mechanisms that regulate the contrast response of neurons in the primate lateral geniculate nucleus.

SG Solomon, JW Peirce, N Dhruv, P Lennie. (2004) Neuron . Profound Contrast Adaptation Early in the Visual Pathway

In the news: for a comment on Solomon et al. (2004) see Baccus and Meister "Retina vs. cortex; contrast adaptation in parallel visual pathways"

SPATIAL CONTEXT

Nerve cells early in the visual pathway are usually thought to be small and simple. We have shown that many of them are sensitive to a larger fraction of visual space than usually thought. This makes the signals of these nerve cells sensitive to the global spatial structure of images, helping make sensory processing more efficient.

Selected publications:

G De Franceschi, SG Solomon (2020) eNeuro. Dynamic Contextual Modulation in Superior Colliculus of Awake Mouse

DA Protti, S Di Marco, JY Huang, CR Vonhoff, V Nguyen, SG Solomon (2014) Journal of physiology. Inner retinal inhibition shapes the receptive field of retinal ganglion cells in primate.

Webb, B.S., Dhruv, N.T., Solomon, S.G., Tailby, C. and Lennie, P. (2005) Journal of Neuroscience. Early and late mechanisms of surround suppression in striate cortex of macaque

Solomon, S.G., White, A.J.R. and Martin, P.R. (2002) Journal of Neuroscience Extraclassical receptive field properties of parvocellular, magnocellular, and koniocellular cells in the primate lateral geniculate nucleus

In the news: for a comment on Webb et al. see Matthew Smith (2006) "Surround suppression in the early visual system"

In the news: for a comment on Martin et al. (2001) see Andrew Derrington (2001) Why do colours fade at the edges?