Book Review: Fall
Bianca Jones Marlin Books, Et Al. Science (2019)
In his latest novel, Fall, Neal Stephenson tells the story of Richard Forthrast, better known as “Dodge,” a video game magnate who has willed his brain to research in the hopes of being reanimated. Heeding the call of the “Eutropians,” Dodge and seven others lead the charge for digital immortality, foretelling the emergence of new technology that will upload the brain of the financial elite to a virtual cloud. But what happens when a human-generated simulation begins to replicate the chaos by which life arose?
With Joseph Jones Marlin
Sex-Specific Differences in Oxytocin Receptor Expression and Function for Parental Behavior
Mitre M., Kranz T.M., Marlin B.J., Schiavo J.K.., Erdjument-Bromage H., Zhang X., Minder J., Neubert T.A., Hackett T.A., Chao M.V., Froemke R.C. Gender and the Genome (2017) 1(4), 142-166.
Parental care is among the most profound behavior expressed by humans and other animals. Despite intense interest in understanding the biological basis of parental behaviors, it remains unknown how much of parenting is encoded by the genome and which abilities instead are learned or can be refined by experience. One critical factor at the intersection between innate behaviors and experience-dependent learning is oxytocin, a neurohormone important for maternal physiology and neuroplasticity. Oxytocin acts throughout the body and brain to promote prosocial and maternal behaviors and modulates synaptic transmission to affect neural circuit dynamics. Recently we developed specific antibodies to mouse oxytocin receptors, found that oxytocin receptors are left lateralized in female auditory cortex, and examined how oxytocin enables maternal behavior by sensitizing the cortex to infant distress sounds. In this study we compare oxytocin receptor expression and function in male and female mice. Receptor expression is higher in adult female left auditory cortex than in right auditory cortex or males. Developmental profiles and mRNA expression were comparable between males and females. Behaviorally, male and female mice began expressing parental behavior similarly after cohousing with experienced females; however, oxytocin enhanced parental behavior onset in females but not males. This suggests that left lateralization of oxytocin receptor expression in females provides a mechanism for accelerating maternal behavior onset, although male mice can also effectively co-parent after experience with infants. The sex-specific pattern of oxytocin receptor expression might genetically predispose female cortex to respond to infant cues, which both males and females can also rapidly learn.
Oxytocin modulation of neural circuits for social behavior
Marlin B.J., Froemke R.C. Oxytocin modulation of neural circuits for social behavior. Developmental Neurobiology (2017) 77, 169-189
Oxytocin is a hypothalamic neuropeptide that has gained attention for the effects on social behavior. Recent findings shed new light on the mechanisms of oxytocin in synaptic plasticity and adaptively modifying neural circuits for social interactions such as conspecific recognition, pair bonding, and maternal care. Here, we review several of these newer studies on oxytocin in the context of previous findings, with an emphasis on social behavior and circuit plasticity in various brain regions shown to be enriched for oxytocin receptors. We provide a framework that highlights current circuit-level mechanisms underlying the widespread action of oxytocin.
A Distributed Network for Social Cognition Enriched for Oxytocin Receptors
Mitre M., Marlin B.J., Schiavo J., Morina E., Norden S., Hackett T.A., Aoki C., Chao M., Froemke R.C. A Distributed Network for Social Cognition Enriched for Oxytocin Receptors. The Journal of Neuroscience (2016) 36, 2517-2535
Oxytocin is a neuropeptide important for social behaviors such as maternal care and parent–infant bonding. It is believed that oxytocin receptor signaling in the brain is critical for these behaviors, but it is unknown precisely when and where oxytocin receptors are expressed or which neural circuits are directly sensitive to oxytocin. To overcome this challenge, we generated specific antibodies to the mouse oxytocin receptor and examined receptor expression throughout the brain. We identified a distributed network of female mouse brain regions for maternal behaviors that are especially enriched for oxytocin receptors, including the piriform cortex, the left auditory cortex, and CA2 of the hippocampus. Electron microscopic analysis of the cerebral cortex revealed that oxytocin receptors were mainly expressed at synapses, as well as on axons and glial processes. Functionally, oxytocin transiently reduced synaptic inhibition in multiple brain regions and enabled long-term synaptic plasticity in the auditory cortex. Thus modulation of inhibition may be a general mechanism by which oxytocin can act throughout the brain to regulate parental behaviors and social cognition.
Oxytocin enables maternal behaviour by balancing cortical inhibition
Marlin B.J., Mitre M., D’amour J.A., Chao M.V., Froemke R.C. Oxytocin enables maternal behaviour by balancing cortical inhibition. Nature (2015) 520, 499-504
Oxytocin is important for social interactions and maternal behaviour. However, little is known about when, where and how oxytocin modulates neural circuits to improve social cognition. Here we show how oxytocin enables pup retrieval behaviour in female mice by enhancing auditory cortical pup call responses. Retrieval behaviour required the left but not right auditory cortex, was accelerated by oxytocin in the left auditory cortex, and oxytocin receptors were preferentially expressed in the left auditory cortex. Neural responses to pup calls were lateralized, with co-tuned and temporally precise excitatory and inhibitory responses in the left cortex of maternal but not pup-naive adults. Finally, pairing calls with oxytocin enhanced responses by balancing the magnitude and timing of inhibition with excitation. Our results describe fundamental synaptic mechanisms by which oxytocin increases the salience of acoustic social stimuli. Furthermore, oxytocin-induced plasticity provides a biological basis for lateralization of auditory cortical processing.
Development of auditory cortical synaptic receptive fields
Froemke R.C., Jones B.J. Development of auditory cortical synaptic receptive fields. Neuroscience and Biobehavioral Reviews (2011) 35, 2105-2113
The central nervous system is plastic throughout life, but is most sensitive to the statistics of the sensory environment during critical periods of early postnatal development. In the auditory cortex, various forms of acoustic experience have been found to shape the formation of receptive fields and influence the overall rate of cortical organization. The synaptic mechanisms that control cortical receptive field plasticity are beginning to be described, particularly for frequency tuning in rodent primary auditory cortex. Inhibitory circuitry plays a major role in critical period regulation, and new evidence suggests that the formation of excitatory–inhibitory balance determines the duration of critical period plasticity for auditory cortical frequency tuning. Cortical inhibition is poorly tuned in the infant brain, but becomes co-tuned with excitation in an experience-dependent manner over the first postnatal month. We discuss evidence suggesting that this may be a general feature of the developing cortex, and describe the functional implications of such transient excitatory–inhibitory imbalance.