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Crossmodal Plasticity, Sensory Experience, and Cognition  

Valeria Vinogradova and Velia Cardin

Crossmodal plasticity occurs when sensory regions of the brain adapt to process sensory inputs from different modalities. This is seen in cases of congenital and early deafness and blindness, where, in the absence of their typical inputs, auditory and visual cortices respond to other sensory information. Crossmodal plasticity in deaf and blind individuals impacts several cognitive processes, including working memory, attention, switching, numerical cognition, and language. Crossmodal plasticity in cognitive domains demonstrates that brain function and cognition are shaped by the interplay between structural connectivity, computational capacities, and early sensory experience.


The Natural Scene Network  

Diane Beck and Dirk B. Walther

Interest in the neural representations of scenes centered first on the idea that the primate visual system evolved in the context of natural scene statistics, but with the advent of functional magnetic resonance imaging, interest turned to scenes as a category of visual representation distinct from that of objects, faces, or bodies. Research comparing such categories revealed a scene network comprised of the parahippocampal place area, the medial place area, and the occipital place area. The network has been linked to a variety of functions, including navigation, categorization, and contextual processing. Moreover, much is known about both the visual representations of scenes within the network as well as its role in and connections to the brain’s semantic system. To fully understand the scene network, however, more work is needed to both break it down into its constituent parts and integrate what is known into a coherent system or systems.


Neural Processing of Speech Using Intracranial Electroencephalography: Sound Representations in the Auditory Cortex  

Liberty S. Hamilton

When people listen to speech and other natural sounds, their brains must take in a noisy acoustic signal and transform it into a robust mapping that eventually helps them communicate and understand the world around them. People hear what was said, who said it, and how they said it, and each of these aspects is encoded in brain activity across different auditory regions. Intracranial recordings in patients with epilepsy, also called electrocorticography or stereoelectroencephalography, have provided a unique window into understanding these processes at a high spatiotemporal resolution. These intracranial recordings are typically performed during clinical treatment for drug-resistant epilepsy or to monitor brain function during neurosurgery. The access to direct recordings of activity in the human brain is a benefit of this method, but it comes with important caveats. Research using intracranial recordings has uncovered how the brain represents acoustic information, including frequency, spectrotemporal modulations, and pitch, and how that information progresses to more complex representations, including phonological information, relative pitch, and prosody. In addition, intracranial recordings have been used to uncover the role of attention and context on top-down modification of perceptual information in the brain. Finally, research has shown both overlapping and distinct brain responses for speech and other natural sounds such as music.


Understanding How Humans Learn and Adapt to Changing Environments  

Daphne Bavelier and Aaron Cochrane

Compared to other animals or to artificial agents, humans are unique in the extent of their abilities to learn and adapt to changing environments. When focusing on skill learning and model-based approaches, learning can be conceived as a progression of increasing, then decreasing, dimensions of representing knowledge. First, initial learning demands exploration of the learning space and the identification of the relevant dimensions for the novel task at hand. Second, intermediate learning requires a refinement of these relevant dimensions of knowledge and behavior to continue improving performance while increasing efficiency. Such improvements utilize chunking or other forms of dimensionality reduction to diminish task complexity. Finally, late learning ensures automatization of behavior through habit formation and expertise development, thereby reducing the need to effortfully control behavior. While automatization greatly increases efficiency, there is also a trade-off with the ability to generalize, with late learning tending to be highly specific to the learned features and contexts. In each of these phases a variety of interacting factors are relevant: Declarative instructions, prior knowledge, attentional deployment, and cognitive fitness have unique roles to play. Neural contributions to processes involved also shift from earlier to later points in learning as effortfulness initially increases and then gives way to automaticity. Interestingly, video games excel at providing uniquely supportive environments to guide the learner through each of these learning stages. This fact makes video games a useful tool for both studying learning, due to their engaging nature and dynamic range of complexity, as well as engendering learning in domains such as education or cognitive training.


Functional Specialization Across the Visual Cortex  

Erez Freud, Tzvi Ganel, and Galia Avidan

Vision is the most important sensory modality for humans, serving a range of fundamental daily behaviors from recognizing objects, people, places, and actions to navigation and visually guided interactions with objects and other individuals. One of the most prominent accounts of cortical functional specialization implies that the visual cortex is segregated into two pathways. The ventral pathway originates from the early visual cortex in the occipital lobe and projects to the inferior surface of the temporal cortex, and it mediates vision for perception. The dorsal pathway extends from the occipital lobe to the posterior portion of the parietal cortex, and it mediates vision for action. This key characterization of the visual system is supported by classic neuropsychological, behavioral, and neuroimaging evidence. Recent research offers new insights on the developmental trajectory of this dissociation as well as evidence for interactions between the two pathways. Importantly, an emerging hypothesis points to the existence of a third visual pathway located on the lateral surface of the ventral pathway and its potential roles in action recognition and social cognition.


Visual Perception in the Human Brain: How the Brain Perceives and Understands Real-World Scenes  

Clemens G. Bartnik and Iris I. A. Groen

How humans perceive and understand real-world scenes is a long-standing question in neuroscience, cognitive psychology, and artificial intelligence. Initially, it was thought that scenes are constructed and represented by their component objects. An alternative view proposed that scene perception starts by extracting global features (e.g., spatial layout) first and individual objects in later stages. A third framework focuses on how the brain not only represents objects and layout but how this information combines to allow determining possibilities for (inter)action that the environment offers us. The discovery of scene-selective regions in the human visual system sparked interest in how scenes are represented in the brain. Experiments using functional magnetic resonance imaging show that multiple types of information are encoded in the scene-selective regions, while electroencephalography and magnetoencephalography measurements demonstrate links between the rapid extraction of different scene features and scene perception behavior. Computational models such as deep neural networks offer further insight by how training networks on different scene recognition tasks results in the computation of diagnostic features that can then be tested for their ability to predict activity in human brains when perceiving a scene. Collectively, these findings suggest that the brain flexibly and rapidly extracts a variety of information from scenes using a distributed network of brain regions.


Drosophila Reward Circuits  

John S. Hernandez, Tariq M. Brown, and Karla R. Kaun

The ability to sense and respond to a rewarding stimulus is a key advantage for animals in their natural environment. The circuits that mediate these responses are complex, and it has been difficult to identify the fundamental principles of reward structure and function. However, the well-characterized brain anatomy and sophisticated neurogenetic tools in Drosophila melanogaster make the fly an ideal model to understand the mechanisms through which reward is encoded. Drosophila find food, water, intoxicating substances, and social acts rewarding. Basic monoaminergic neurotransmitters, including dopamine (DA), serotonin (5-HT), and octopamine (OA), play a central role in encoding these rewards. DA is central to sensing, encoding, responding, and predicting reward, whereas 5-HT and OA carry information about the environment that influences DA circuit activity. In contrast, slower-acting neuromodulators such as hormones and neuropeptides play a key role in both encoding the pleasurable stimulus and modulating how the internal environment of the fly influences reward sensation and seeking. Recurring circuit motifs for reward signaling identified in Drosophila suggest that these key principles will help elucidate understanding of how reward circuits function in all animals.


Magnetoreception and Bird Navigation  

Roswitha Wiltschko and Wolfgang Wiltschko

The magnetic field of the earth provides birds with navigational information, with birds having two different receptor systems, one for the direction, the other for the intensity of the geomagnetic field. The direction of the geomagnetic field is used as a compass, with the avian magnetic compass being an inclination compass not recording the polarity of the field. The respective directional information is perceived by light-dependent radical pair processes in the eyes, with cryptochrome, a photopigment with the chromophore flavin adenine dinucleotide as receptor molecule. It is transmitted by the optic nerve to the brain, where it is processed by parts of the visual system. The magnetic compass not only serves to orient avian flights but also acts as a reference system for route reversal, calibrating the astronomical compass systems, and in migratory birds, as reference for the innate information on the migratory direction. Magnetic intensity and inclination that show gradients from the poles to the magnetic equator are part of the mechanisms that allow birds to determine their position. Intensity is perceived by receptors based on magnetite, a permanently magnetic material. The effect of a brief, strong magnetic pulse and its duration indicates that superparamagnetic particles are involved. The respective information is transmitted by the ophthalmic branch of the trigeminal nerve to the trigeminal brainstem complex in the brain. Testing birds in magnetic fields of a distant site, i.e., magnetically simulating a displacement, documents that magnetic intensity and inclination are very most important components of the navigational “map” that enables birds to determine their position relative to the goal and thus derive the compass course leading to this goal. Furthermore, certain magnetic conditions act as signposts and elicit specific spontaneous responses.


Pain and Its Modulation  

Asaf Keller

Sensory perceptions are inherently subjective, being influenced by factors such as expectation, attention, affect, and past experiences. Nowhere is this more commonly experienced than with the perception of pain, whose perceived intensity and emotional impact can fluctuate rapidly. The perception of pain in response to the same nociceptive signal can also vary substantially between individuals. Pain is not only a sensory experience. It also involves profound affective and cognitive dimensions, reflecting the activation of and interactions among multiple brain regions. The modulation of pain perception by such interactions has been most extensively characterized in the context of the “descending pain modulatory system.” This system includes a variety of pathways that directly or indirectly modulate the activity of neurons in the spinal dorsal horn, the second-order neurons that receive inputs directly from nociceptors. Less understood are the interactions among brain regions that modulate the affective and cognitive aspects of pain perception. Emerging data suggest that certain pain conditions result from dysfunction in pain modulation, suggesting that targeting these dysfunctions might have therapeutic value. Some therapies that are thought to target pain modulation pathways—such as cognitive behavior therapy, mindfulness-based stress reduction, and placebo analgesia—are safer and less expensive than pharmacologic or surgical approaches, further emphasizing the importance of understanding these modulatory mechanisms. Understanding the mechanisms through which pain modulation functions may also illuminate fundamental mechanisms of perception and consciousness.


The Sensory World of the Naked Mole-Rat  

Thomas J. Park

Naked mole-rats are subterranean mammals that are native to equatorial east Africa including Ethiopia, Somalia, and Kenya. They are unusual among subterranean mammals in that they live in very large colonies where many respiring animals deplete oxygen and overproduce carbon dioxide. Some of their sensory traits, such as poor vision and hearing, are considered typical of subterranean mammals. However, naked mole-rats display three sensory traits that are unusual even among subterranean mammals. First, they possess a sensitive sensory array of body vibrissae on their otherwise furless bodies. Second, they have a greatly reduced sense of inflammatory and chemical pain, but express acute mechanical and thermal pain. Third, naked mole-rats, and likely other African mole-rat species, are the only rodents known that show no postbirth growth of the vomeronasal organ, an organ associated with sensing pheromones. These sensory traits, along with extreme tolerance to hypoxia and resistance to cancer, make the naked mole-rat an important animal model for studying sensory systems as well as in multiple other scientific fields.