A. David Milner

Bio: A. David Milner is an academic researcher from Durham University. The author has contributed to research in topics: Visual agnosia & Vision for perception and vision for action. The author has an hindex of 36, co-authored 82 publications receiving 13707 citations. Previous affiliations of A. David Milner include University of St Andrews & University of Edinburgh.

The visual brain in action

Abstract: Prologue 1. Introduction: vision from a biological point of view 2. Visual processing in the primate visual cortex 3. 'Cortical blindness' 4. Disorders of spatial perception and the visual control of action 5. Disorders of visual recognition 6. Dissociations between perception and action in normal subjects 7. Attention, consciousness, and the coordination of behaviour 8. Epilogue: twelve years on

Ventral occipital lesions impair object recognition but not object-directed grasping: an fMRI study.

Abstract: Summary D.F., a patient with severe visual form agnosia, has been the subject of extensive research during the past decade. The fact that she could process visual input accurately for the purposes of guiding action despite being unable to perform visual discriminations on the same visual input inspired a novel interpretation of the functions of the two main cortical visual pathways or ‘streams’. Within this theoretical context, the authors proposed that D.F. had suffered severe bilateral damage to her occipitotemporal visual system (the ‘ventral stream’), while retaining the use of her occipitoparietal visual system (the ‘dorsal stream’). The present paper reports a direct test of this idea, which was initially derived from purely behavioural data, before the advent of modern functional neuroimaging. We used functional MRI to examine activation in her ventral and dorsal streams during object recognition and object-directed grasping tasks. We found that D.F. showed no difference in activation when presented with line drawings of common objects compared with scrambled line drawings in the lateral occipital cortex (LO) of the ventral stream, an area that responded differentially to these stimuli in healthy individuals. Moreover, highresolution anatomical MRI showed that her lesion corresponded bilaterally with the location of LO in healthy participants. The lack of activation with line drawings in D.F. mirrors her poor performance in identifying the objects depicted in the drawings. With coloured and greyscale pictures, stimuli that she can identify more often, D.F. did show some ventral-stream activation. These activations were, however, more widely distributed than those seen in control participants and did not include LO. In contrast to the absent or abnormal activation observed during these perceptual tasks, D.F. showed robust activation in the expected dorsal stream regions during object grasping, despite considerable atrophy in some regions of the parietal lobes. In particular, an area in the anterior intraparietal sulcus was activated more for grasping an object than for just reaching to that object, for both D.F. and controls. In conclusion, we have been able to confirm directly that D.F.’s visual form agnosia is associated with extensive damage to the ventral stream, and that her spared visuomotor skills are associated with visual processing in the dorsal stream.

Chapter 28 Visual pathways to perception and action

Abstract: Publisher Summary There appears to be important integrative areas within the superior temporal sulcus in the monkey where a great deal of the necessary interaction to ensure behavioral and perceptual unity. Indeed there are many polysensory neurons in these areas, such that not only visual but also cross-modal perceptual integration may be enabled by these networks. Despite the crosstalk between the dorsal and ventral streams, the chapter discusses that each stream uses visual information in different ways. Both streams process information about orientation and shape, and probably about spatial relationships, including depth; and both are subject to the modulatory influences of an animal's shifting spatial attention. The ventral stream provide object-centered coding, while the dorsal provide entirely viewer-centered information: the former would enable a monkey to identify an object as being of an edible type, the latter to guide its actions in picking it up. Although there will be differences in the ways that visual information is processed in the two systems, these differences are not a reflection of some biologically arbitrary separation of inputs, but rather a consequence of the special transformations required for perception and action, respectively.

Sight Unseen: An Exploration of Conscious and Unconscious Vision

Abstract: Prologue 1. A tragic accident 2. Doing without seeing 3. When vision for action fails 4. The origins of vision: from modules to models 5. Streams within streams 6. Why do we need two systems? 7. Getting it all together 8. Postscript: Dee's life 15 years on Epilogue

Chapter 11 Working memory

Abstract: Publisher Summary This chapter focuses on the modern notion of short-term memory, called working memory. Working memory refers to the temporary maintenance of information that was just experienced or just retrieved from long-term memory but no longer exists in the external environment. These internal representations are short-lived, but can be maintained for longer periods of time through active rehearsal strategies, and can be subjected to various operations that manipulate the information in such a way that makes it useful for goal-directed behavior. Working memory is a system that is critically important in cognition and seems necessary in the course of performing many other cognitive functions, such as reasoning, language comprehension, planning, and spatial processing. This chapter demonstrates the functional importance of dopamine to working memory function in several ways. Elucidation of the cognitive and neural mechanisms underlying human working memory is an important focus of cognitive neuroscience and neurology for much of the past decade. One conclusion that arises from research is that working memory, a faculty that enables temporary storage and manipulation of information in the service of behavioral goals, can be viewed as neither a unitary, nor a dedicated system. Data from numerous neuropsychological and neurophysiological studies in animals and humans demonstrates that a network of brain regions, including the prefrontal cortex, is critical for the active maintenance of internal representations.

Two-Stream Convolutional Networks for Action Recognition in Videos

Abstract: We investigate architectures of discriminatively trained deep Convolutional Networks (ConvNets) for action recognition in video. The challenge is to capture the complementary information on appearance from still frames and motion between frames. We also aim to generalise the best performing hand-crafted features within a data-driven learning framework. Our contribution is three-fold. First, we propose a two-stream ConvNet architecture which incorporates spatial and temporal networks. Second, we demonstrate that a ConvNet trained on multi-frame dense optical flow is able to achieve very good performance in spite of limited training data. Finally, we show that multitask learning, applied to two different action classification datasets, can be used to increase the amount of training data and improve the performance on both. Our architecture is trained and evaluated on the standard video actions benchmarks of UCF-101 and HMDB-51, where it is competitive with the state of the art. It also exceeds by a large margin previous attempts to use deep nets for video classification.

Place navigation impaired in rats with hippocampal lesions.

Abstract: Electrophysiological studies have shown that single cells in the hippocampus respond during spatial learning and exploration1–4, some firing only when animals enter specific and restricted areas of a familiar environment. Deficits in spatial learning and memory are found after lesions of the hippocampus and its extrinsic fibre connections5,6 following damage to the medial septal nucleus which successfully disrupts the hippocampal theta rhythm7, and in senescent rats which also show a correlated reduction in synaptic enhancement on the perforant path input to the hippocampus8. We now report, using a novel behavioural procedure requiring search for a hidden goal, that, in addition to a spatial discrimination impairment, total hippocampal lesions also cause a profound and lasting placenavigational impairment that can be dissociated from correlated motor, motivational and reinforcement aspects of the procedure.