Martin Chadwick

Google DeepMind

The philosopher John Rawls proposed the Veil of Ignorance (VoI) as a thought experiment to identify fair principles for governing a society. Here, we apply the VoI to an important governance domain: artificial intelligence (AI). In five incentive-compatible studies (N = 2, 508), including two preregistered protocols, participants choose principles...

Collective action demands that individuals efficiently coordinate how much, where, and when to cooperate. Laboratory experiments have extensively explored the first part of this process, demonstrating that a variety of social-cognitive mechanisms influence how much individuals choose to invest in group efforts. However, experimental research has be...

In this issue of Neuron, Cross et. al (2021) • Cross L. • Cockburn J. • Yue Y. • O’Doherty J.P. Using deep reinforcement learning to reveal how the brain encodes abstract state-space representations in high-dimensional environments. Neuron. 2021; 109 ( this issue) : 724-738 • Google Scholar use a deep reinforcement learning algorithm to underst...

Recent research developing neural network architectures with external memory have often used the benchmark bAbI question and answering dataset which provides a challenging number of tasks requiring reasoning. Here we employed a classic associative inference task from the memory-based reasoning neuroscience literature in order to more carefully prob...

Recent evidence challenges the widely held view that the hippocampus is specialized for episodic memory, by demonstrating that it also underpins the integration of information across experiences. Contemporary computational theories propose that these two contrasting functions can be accomplished by big-loop recurrence, whereby the output of the sys...

Author summary Our past experiences are captured in autobiographical memories that allow us to recollect events from our lives long after they originally occurred. A part of the brain’s frontal lobe, called the ventromedial prefrontal cortex (vmPFC), is known to be important for supporting autobiographical memories, especially as memories become mo...

RSM of within- and between-time-point pattern similarity values for Experiment 1. Each cell in this matrix contains the group mean pattern similarity score between memories from all sampled time points, averaged across the two memory sets. The values along the diagonal represent the within-memory similarity for each time point. Off-diagonal values...

Within- versus between-time-point pattern similarity for Experiment 1. Time-dependent changes in neural representation scores were driven by within- rather than between-memory scores (see S9 Data for individual participant numerical values). (TIFF)

Individual participant values underlying Fig 5. (XLSX)

Neural representation scores (mean, SD) for other brain regions in Experiment 1 (n = 30). (DOCX)

Behavioural data (mean, SD) for Experiment 2 (n = 16). Subjective ratings of memory characteristics and objective ratings of memory content for Experiment 2 (relates to Figs 6 and 7). (DOCX)

Individual participant values underlying Fig 2. (XLSX)

Individual participant values underlying S2 Table. (XLSX)

Behavioural data (mean, SD) for Experiment 1 (n = 30). Subjective ratings of memory characteristics and objective ratings of memory content for Experiment 1 (relates to Figs 1 and 2). (DOCX)

Box plot of neural representation scores for Experiment 1. Boxes represent 25th to 75th percentiles around the median; whiskers represent minimum and maximum values; means are indicated by solid circles (see S8 Data for individual participant numerical values). (TIFF)

Results of the group vmPFC searchlight analysis in MNI space for Experiment 1. (A) Colour-coded areas represent the FWE-corrected T-statistic in which within-memory detectability was higher than between-memory detectability across participants. (B) Comparison of memory detectability across time points within this functionally defined area, showing...

Individual participant values underlying Fig 6B–6F. (XLSX)

Individual participant values underlying Fig 8. (XLSX)

Individual participant values underlying S4B Fig. (XLSX)

Individual participant values underlying Fig 1B–1F. (XLSX)

Individual participant values underlying Fig 4. (XLSX)

Individual participant values underlying Fig 7. (XLSX)

Individual participant values underlying S3 Fig. (XLSX)

Individual participant additional subjective ratings from Experiment 1. (XLSX)

Individual participant values underlying S2 Fig. (XLSX)

Individual participant additional subjective ratings from Experiment 2. (XLSX)

Systems-level consolidation refers to the time-dependent reorganisation of memory traces in the neocortex, a process in which the ventromedial prefrontal cortex (vmPFC) has been implicated. Capturing the precise temporal evolution of this crucial process in humans has long proved elusive. Here, we used multivariate methods and a longitudinal functi...

Deep neural networks have achieved impressive successes in fields ranging from object recognition to complex games such as Go. Navigation, however, remains a substantial challenge for artificial agents, with deep neural networks trained by reinforcement learning failing to rival the proficiency of mammalian spatial behaviour, which is underpinned b...

Neonatal hypoxia can lead to hippocampal atrophy, which can lead, in turn, to memory impairment. To test the generalisability of this causal sequence, we examined a cohort of 41 children aged 8-16, who, having received the arterial switch operation to correct for transposition of the great arteries, had sustained significant neonatal cyanosis but w...

Significance False memories can arise in daily life through a mixture of factors, including misinformation and prior conceptual knowledge. This can have serious consequences in settings, such as legal eyewitness testimony, which depend on the accuracy of memory. We investigated the brain basis of false memory with fMRI, and found that patterns of a...

Increasing evidence is emerging for sexual dimorphism in the trajectory of white matter development in children assessed using volumetric MRI and more recently diffusion MRI. Recent studies using diffusion MRI have examined cohorts with a wide age range (typically between 5 and 30 years) showing focal regions of differential diffusivity and fractio...

Each of us has a rich set of autobiographical memories that provides us with a coherent story of our lives. These memories are known to be highly structured both thematically and temporally. However, it is not known how we naturally tend to explore the mental timeline of our memories. Here we developed a novel cued retrieval paradigm in order to in...

The optic radiation (OR) is a component of the visual system known to be myelin mature very early in life. Diffusion tensor imaging (DTI) and its unique ability to reconstruct the OR in vivo were used to study structural maturation through analysis of DTI metrics in a cohort of 90 children aged 5-18 years. As the OR is at risk of damage during epil...

Navigating to a safe place, such as a home or nest, is a fundamental behavior for all complex animals. Determining the direction to such goals is a crucial first step in navigation. Surprisingly, little is known about how or where in the brain this "goal direction signal" is represented. In mammals, "head-direction cells" are thought to support thi...

Intelligent action entails exploiting predictions about associations between elements of ones environment. The hippocampus and mediotemporal cortex are endowed with the network topology, physiology, and neurochem-istry to automatically and sparsely code sensori-cognitive associations that can be reconstructed from single or partial inputs. Whilst a...

Retrosplenial cortex neurons provide a signal akin to a compass readout. Evidence in humans now demonstrates that these neurons anchor their representations locally, locking to the geometry of a room rather than to the city beyond.

Significance How does the brain allow us to recall numerous life experiences despite there often being a high degree of similarity between memories? This is a key question in neuroscience. Moreover, there is also keen interest in understanding why some people are able to recall memories with greater clarity than other people. In this study, we iden...

The hippocampus has long been implicated in supporting autobiographical memories, but little is known about how they are instantiated in hippocampal subfields. Using high resolution functional MRI combined with multi-voxel pattern analysis we found it was possible to detect representations of specific autobiographical memories in individual hippoca...

Assessing the functional reserve of key memory structures in the medial temporal lobes (MTL) of pre-surgical patients with intractable temporal lobe epilepsy (TLE) remains a challenge. Conventional functional MRI (fMRI) memory paradigms have yet to fully convince of their ability to confidently assess the risk of a post-surgical amnesia. An alterna...

Boundary extension (BE) is a pervasive phenomenon whereby people remember seeing more of a scene than was present in the physical input, because they extrapolate beyond the borders of the original stimulus. This automatic embedding of a scene into a wider context supports our experience of a continuous and coherent world, and is therefore highly ad...

How autobiographical memories are represented in the human brain and whether this changes with time are questions central to memory neuroscience. Two regions in particular have been consistently implicated, the ventromedial prefrontal cortex (vmPFC) and the hippocampus, although their precise contributions are still contested. The key question in t...

A complete understanding of the hippocampus depends on elucidating the representations and computations that exist in its anatomically distinct subfields. High-resolution structural and functional MRI scanning is starting to permit insights into hippocampal subfields in humans. In parallel, such scanning has facilitated the use of multi-voxel patte...

Multi-voxel pattern analysis (MVPA), or 'decoding', of fMRI activity has gained popularity in the neuroimaging community in recent years. MVPA differs from standard fMRI analyses by focusing on whether information relating to specific stimuli is encoded in patterns of activity across multiple voxels. If a stimulus can be predicted, or decoded, sole...

Recent theoretical perspectives have suggested that the function of the human hippocampus, like its rodent counterpart, may be best characterized in terms of its information processing capacities. In this study, we use a combination of high-resolution functional magnetic resonance imaging, multivariate pattern analysis, and a simple decision making...

To re-examine whether or not selective hippocampal damage reduces novelty preference in visual paired comparison (VPC), we presented two different versions of the task to a group of patients with developmental amnesia (DA), each of whom sustained this form of pathology early in life. Compared with normal control participants, the DA group showed a...

The hippocampus is proposed to process overlapping episodes as discrete memory traces, although direct evidence for this in human episodic memory is scarce. Using green-screen technology we created four highly overlapping movies of everyday events. Participants were scanned using high-resolution fMRI while recalling the movies. Multivariate pattern...

The white matter of the brain undergoes a range of structural changes throughout development; from conception to birth, in infancy, and onwards through childhood and adolescence. Several studies have used diffusion magnetic resonance imaging (dMRI) to investigate these changes, but a consensus has not yet emerged on which white matter tracts underg...

In recent years, multivariate pattern analyses have been performed on functional magnetic resonance imaging (fMRI) data, permitting prediction of mental states from local patterns of blood oxygen-level-dependent (BOLD) signal across voxels. We previously demonstrated that it is possible to predict the position of individuals in a virtual-reality en...

Brain development continues actively during adolescence. Previous MRI studies have shown complex patterns of apparent loss of grey matter (GM) volume and increases in white matter (WM) volume and fractional anisotropy (FA), an index of WM microstructure. In this longitudinal study (mean follow-up=2.5+/-0.5 years) of 24 adolescents, we used a voxel-...