Mnemonic Structures Research Articles

A corollary discharge mediates saccade-related inhibition of single units in mnemonic structures of the human brain

Despite the critical link between visual exploration and memory, little is known about how neuronal activity in the human mesial temporal lobe (MTL) is modulated by saccades. Here, we characterize saccade-associated neuronal modulations, unit-by-unit, and contrast them to image onset and to occipital lobe neurons. We reveal evidence for a corollary discharge (CD)-like modulatory signal that accompanies saccades, inhibiting/exciting a unique population of broad-/narrow-spiking units, respectively, before and during saccades and with directional selectivity. These findings comport well with the timing, directional nature, and inhibitory circuit implementation of a CD. Additionally, by linking neuronal activity to event-related potentials (ERPs), which are directionally modulated following saccades, we recontextualize the ERP associated with saccades as a proxy for both the strength of inhibition and saccade direction, providing a mechanistic underpinning for the more commonly recorded saccade-related ERP in the human brain.

Volitional control of individual neurons in the human brain.

Brain-machine interfaces allow neuroscientists to causally link specific neural activity patterns to a particular behaviour. Thus, in addition to their current clinical applications, brain-machine interfaces can also be used as a tool to investigate neural mechanisms of learning and plasticity in the brain. Decades of research using such brain-machine interfaces have shown that animals (non-human primates and rodents) can be operantly conditioned to self-regulate neural activity in various motor-related structures of the brain. Here, we ask whether the human brain, a complex interconnected structure of over 80 billion neurons, can learn to control itself at the most elemental scale-a single neuron. We used the unique opportunity to record single units in 11 individuals with epilepsy to explore whether the firing rate of a single (direct) neuron in limbic and other memory-related brain structures can be brought under volitional control. To do this, we developed a visual neurofeedback task in which participants were trained to move a block on a screen by modulating the activity of an arbitrarily selected neuron from their brain. Remarkably, participants were able to volitionally modulate the firing rate of the direct neuron in these previously uninvestigated structures. We found that a subset of participants (learners), were able to improve their performance within a single training session. Successful learning was characterized by (i) highly specific modulation of the direct neuron (demonstrated by significantly increased firing rates and burst frequency); (ii) a simultaneous decorrelation of the activity of the direct neuron from the neighbouring neurons; and (iii) robust phase-locking of the direct neuron to local alpha/beta-frequency oscillations, which may provide some insights in to the potential neural mechanisms that facilitate this type of learning. Volitional control of neuronal activity in mnemonic structures may provide new ways of probing the function and plasticity of human memory without exogenous stimulation. Furthermore, self-regulation of neural activity in these brain regions may provide an avenue for the development of novel neuroprosthetics for the treatment of neurological conditions that are commonly associated with pathological activity in these brain structures, such as medically refractory epilepsy.

Theta rhythm supports hippocampus-dependent integrative encoding in schematic/semantic memory networks

Integrating new information into existing schematic/semantic structures of knowledge is the basis of learning in our everyday life as it enables structured representation of information and goal-directed behaviour in an ever-changing environment. However, how schematic/semantic mnemonic structures aid the integration of novel elements remains poorly understood. Here, we showed that the ability to integrate novel picture information into learned structures of picture associations that overlapped by the same picture scene (i.e., simple network) or by a conceptually related picture scene (i.e., schematic/semantic network) is hippocampus-dependent, as patients with lesions at the medial temporal lobe (including the hippocampus) were impaired in inferring novel relations between pictures within these memory networks. We also found more persistent and widespread scalp EEG theta oscillations (3–5 Hz) while participants integrated novel pictures into schematic/semantic memory networks than into simple networks. On the other hand, greater neural similarity was observed between EEG patterns elicited by novel and related events within simple networks than between novel and related events within schematic/semantic memory networks. These findings have important implications for our understanding of the neural mechanisms that support the development and organization of structures of knowledge.

Pedagogic and Dramatic Roles of the Liturgy in Piers Plowman

This essay proposes that William Langland exploited the didactic potential of the liturgy when expounding the Church’s theology in Piers Plowman . After discussing Langland’s knowledge of the liturgy, the focus is on passages where the poem appears to follow liturgical analogues closely, using their rhetorical potential to address complex points of theology and to convey them with clarity. It then discusses how the liturgy influenced literary techniques in Piers Plowman , focusing on narrative, allegory and mnemonic structures. It concludes with a consideration of how liturgical concepts of time make sense of the poem’s meandering course if we think of the dreamer’s inner debates as a network of devotional introspection connected with the services of the Church year over the course of a lifetime.

Bunker auscultation: A classification system for a proto-method of sensory space composition

A subterranean WWII bunker, hidden under the City of Plymouth, is used as the context for the investigation. The enquiry considers the bunker as psychoactive in nature, that is, stimulating a range of psychological, emotional and behavioural responses in relationship to the percipient’s spatial register. The project focuses on developing a classification system, and examines space as a conveying medium. The project acts as a scheme for establishing a critical methodology of sensory space and develops an interdisciplinary architectural language for thinking about architecture as phenomenological constructions, whilst implying a greater understanding of the roles of mnemonic structures.

The Role of Jesus' Opponents in the Markan Drama

Discussions on the possibility that Mark's Gospel may have been modelled, either consciously or subconsciously, on Greek tragic drama have gathered momentum in recent years. It has also been shown that a most important feature of Greek tragedy is the repetitive device of ‘foreshadowing’, a technique which has rightly been seen as essential to the development of mnemonic structures in oral epic. The use of this device in the Bible, it may be argued, is no less pronounced than in Greek drama. C. H. Lohr, in particular, has argued strongly for the presence of foreshadowing in Matthew's Gospel, and it is our purpose here to enquire whether the writer of the Second Gospel, too, was aware of this dramatic device. Matthew achieved the desired effect by means of dream episodes (Matt 1. 20; 2. 12, 13, 19, 22; 27. 19) and the repetition of divine names, especially ‘Son of David’, at strategic points (Matt 9. 27; 12. 23; 15. 22; 20. 30, 31; 22. 43). There are certainly no dream narratives in Mark's Gospel, and even the references to divine titles may seem to have been arranged in a somewhat arbitrary fashion at first glance. On the other hand, it can hardly be denied that we find in Mark's vivid account an inexorable drift towards death: the inevitable shadow of the cross falls across the text even as early as Mark 2. 20 – the disciples may not fast until ‘that day’ when the bridegroom is taken from them. And there is the hint of opposition to Jesus even prior to that! There is little doubt in my mind that Mark was keenly aware of the effective use to which the device of foreshadowing could be put, but his technique differs from that which Lohr has ascribed to Matthew. In true tragic style he wants to emphasise the inevitability of the cross as the omega point of Jesus' destiny, and to do that he uses not dreams or prophecies, but actors who engage Jesus in controversy or conflict at strategic points within the gospel story. It matters to Mark who these actors are, what role they play, and precisely when and where they make their entrances on stage. We shall thus be concerned to show, in the remainder of this paper, how the Evangelist treats the various groups of Jewish opponents as a literary device for foreshadowing Jesus' crucifixion.