Diversity and Homogeneity in Responses of Midbrain Dopamine Neurons

Fiorillo, Christopher D.,Yun, Sora R.,Song, Minryung R. Society for Neuroscience 2013 The Journal of neuroscience Vol.33 No.11

<P>Dopamine neurons of the ventral midbrain have been found to signal a reward prediction error that can mediate positive reinforcement. Despite the demonstration of modest diversity at the cellular and molecular levels, there has been little analysis of response diversity in behaving animals. Here we examine response diversity in rhesus macaques to appetitive, aversive, and neutral stimuli having relative motivational values that were measured and controlled through a choice task. First, consistent with previous studies, we observed a continuum of response variability and an apparent absence of distinct clusters in scatter plots, suggesting a lack of statistically discrete subpopulations of neurons. Second, we found that a group of “sensitive” neurons tend to be more strongly suppressed by a variety of stimuli and to be more strongly activated by juice. Third, neurons in the “ventral tier” of substantia nigra were found to have greater suppression, and a subset of these had higher baseline firing rates and late “rebound” activation after suppression. These neurons could belong to a previously identified subgroup of dopamine neurons that express high levels of H-type cation channels but lack calbindin. Fourth, neurons further rostral exhibited greater suppression. Fifth, although we observed weak activation of some neurons by aversive stimuli, this was not associated with their aversiveness. In conclusion, we find a diversity of response properties, distributed along a continuum, within what may be a single functional population of neurons signaling reward prediction error.</P>

Multiphasic Temporal Dynamics in Responses of Midbrain Dopamine Neurons to Appetitive and Aversive Stimuli

Fiorillo, Christopher D.,Song, Minryung R.,Yun, Sora R. Society for Neuroscience 2013 The Journal of neuroscience Vol.33 No.11

<P>The transient response of dopamine neurons has been described as reward prediction error (RPE), with activation or suppression by events that are better or worse than expected, respectively. However, at least a minority of neurons are activated by aversive or high-intensity stimuli, casting doubt on the generality of RPE in describing the dopamine signal. To overcome limitations of previous studies, we studied neuronal responses to a wider variety of high-intensity and aversive stimuli, and we quantified and controlled aversiveness through a choice task in which macaques sacrificed juice to avoid aversive stimuli. Whereas most previous work has portrayed the RPE as a single impulse or “phase,” here we demonstrate its multiphasic temporal dynamics. Aversive or high-intensity stimuli evoked a triphasic sequence of activation-suppression-activation extending over a period of 40–700 ms. The initial activation at short latencies (40–120 ms) reflected sensory intensity. The influence of motivational value became dominant between 150 and 250 ms, with activation in the case of appetitive stimuli, and suppression in the case of aversive and neutral stimuli. The previously unreported late activation appeared to be a modest “rebound” after strong suppression. Similarly, strong activation by reward was often followed by suppression. We suggest that these “rebounds” may result from overcompensation by homeostatic mechanisms in some cells. Our results are consistent with a realistic RPE, which evolves over time through a dynamic balance of excitation and inhibition.</P>

Two Dimensions of Value: Dopamine Neurons Represent Reward But Not Aversiveness

American Association for the Advancement of Scienc 2013 Science Vol.341 No.6145

<P><B>Coding Reward Versus Punishment</B></P><P>Reinforcement learning is driven by reward prediction error, and a very influential theory has proposed that dopamine neurons provide this signal to teach value to the brain. Although this is called a reward prediction error, it has been assumed to also represent aversiveness. Thus, it was thought that the dopamine signal could be sufficient for learning total value. <B>Fiorillo</B> (p. 546) found that dopamine alone was not sufficient to encode value, implying that there must be an analogous signal for aversiveness.</P>

REVIEW OF THE DINOSAUR RECORD OF ALASKA WITH COMMENTS REGARDING KOREAN DINOSAURS AS COMPARABLE HIGH-LATITUDE FOSSIL FAUNAS

Anthony R. Fiorillo 한국고생물학회 2006 고생물학회지 Vol.22 No.1

알래스카의 공룡화석은 후기 쥐라기에서 백악기까지 산출된다. 후기 쥐라기 공룡화석은 사진 기록으로 두건이 확인되는데 한 건은 일련의 수각류 공룡발자국이고 다른 것은 공룡뼈 조각이다 이들은 모두 알래스카의 남서쪽에서 산출된다. 이와 유사하게 전기 백악기 공룡화석도 잘 알려져 있지 않은데 몇 개의 공룡발자국 산지와 공룡피부흔적이 발견된 곳이 있다. 알래스카에서 더 젊은 지층의 기록은 후기 백악기 전기인 Cenomanian과 Turonian 시기다. 많은 화석지가 발견되고 있으며 이들 화석지의 대부분은 공룡발자국 산지다. 일반적으로 이들 화석지는 알래스카의 북쪽 지역에 한정된다. 발자국 산지의 예외적인 한 곳은 알래스카 남중앙의 해성층에서 발견된 오리주둥이공룡의 뼈와 함께 산출된다. 현재까지 가장 풍부한 공룡화석은 Campanian-Maastrichtian 육성층에서 산출되고 있다. 대부분의 화석지가 북알래스카이지만 새로운 화석지가 남서부 지역과 McKinley산 근처의 중앙 알래스카 산맥에서도 발견되었다. 가장 최후기의 백악기 기록은 많은 뼈화석과 발자국 화석으로 채워진다. 알래스카 백악기에서 산출된 척추동물화석은 경골어류, 거북, 크고 작은 수각류, 조류, 힙실로포돈류, 파키케팔로사우루스류, 곡룡류, 각룡류, 오리주둥이공룡류 그리고 포유류인 multituberculate, 유대류, 태반류 등이다. 이러한 표본들은 강과 강 제방에 묻힌 것으로 발굴을 통해 수집되었다. 한국의 백악기 경상누층군은 다양한 척추화석 기록을 갖고 있다. 비록 경상누층군이 전기 백악기에 더 많은 화석기록을 갖고 있지만 알래스카의 Campanian 시기에 대비되는 화석 기록도 갖고 있다. 고지자기 기록에 의하면 백악기의 알래스카와 한국의 척추동물화석은 고위도 지역의 화석군을 나타내며 이러한 점에서 논의해야 할 필요가 있다. 현재 북극권에는 동식물이 극한 환경에서 삶을 유지하기 위해 독특한 적응을 하고 있다. 백악기의 고위도 기후가 현재보다 더 온순했지만 빛의 강도와 각도 같은 물리적인 요소는 늘 일정했다. 그러므로 이러한 백악기 척추동물화석군은 옛날 고위도 환경에 적응한 생명체에 대한 가치 있는 통찰력을 제공한다. The record of dinosaurs from Alaska extends from the Late Jurassic through the Cretaceous. The record for the Late Jurassic is based on two photographed occurrences of dinosaurs, one a series of theropod tracks and the other a dinosaurian bone fragment. Both records occur in the southwestern part of the state. Similarly dinosaur records for the Early Cretaceous are represented but in very sparse numbers, consisting of a few footprint localities and a dinosaur skin impression locality that is also likely from this interval in time. Younger records of dinosaurs for Alaska also occur in the early Late Cretaceous (Cenomanian and Turonian). Such localities are growing in number and most are footprint localities. Generally these localities are confined to the northern part of the state. One exception to the footprint localities is that of a locality yielding a partial hadrosaur skeleton found in marine rocks in the south-central part of the state. By far the richest record of dinosaurs for the state is from the Campanian-Maastrichtian sequences of non-marine rocks. Whereas most of these localities are from northern Alaska, additional new localities have been found in the southwestern part of the state as well as in the central Alaska Range, near Mt. McKinley. This latest Cretaceous record consists of numerous fossil bone and footprint localities. The fossil vertebrate fauna recovered from Cretaceous rocks in Alaska include specimens of osteichthyan fishes, a chelonian, large and small theropods, birds, a hypsilophodontid, a pachycephalosaur, an ankylosaur, ceratopsians and hadrosaurians, as well as multituberculate, marsupial, and placental mammals. These specimens have been acquired through quarry and site excavations, and accumulated river bar and river bank float. The Cretaceous Gyeongsang Supergroup of Korea contains a comparably rich fossil vertebrate record. Whereas the Gyeongsang Supergroup is more prolific in the Early Cretaceous than the coeval Alaskan record it also contains fossil vertebrates that are correlative with the Campanian record of Alaska. Based on paleomagnetic reconstructions, both the Alaskan Cretaceous vertebrate fauna and the Korean vertebrate fauna represent ancient high-latitude faunas and should be examined in that Light. In the modern Arctic, animals and plants demonstrate suites of unique features for life in extreme environments. Even though global climate in the Cretaceous in the high latitudes was milder than today some physical parameters, such as the quantity and angle of light, likely remained constant through time. Therefore, these Cretaceous vertebrate faunas hold valuable insights into adaptations for life in an ancient high-latitude environment.

A neurocentric approach to Bayesian inference

Nature Publishing Group, a division of Macmillan P 2010 Nature reviews. Neuroscience Vol.11 No.8

Recent Developments in Magnetic Measurements

V. Basso,F. Fiorillo,C. Beatrice,A. Caprile,M. Kuepferling,A. Magni,C. P. Sasso 한국자기학회 2013 Journal of Magnetics Vol.18 No.3

We present a few significant advances in methods and concepts of magnetic measurements, aimed both at providing novel routes in the characterization of hard and soft magnetic materials and at improving our basic knowledge of the magnetization process. We discuss, in particular, investigation methods and experimental arrangements that have been developed in recent times for: 1) Hysteresis loop determination in extra-hard magnets by means of Pulsed Field Magnetometry; 2) Broadband observation of domain wall dynamics by highspeed stroboscopical Kerr techniques; 3) Entropy measurements in magnetocaloric materials by calorimetry in magnetic field. While pertaining to somewhat independent fields of investigation, all these measuring techniques have in common a solid approach to the underlying physical phenomenology and have a potential for further developments.

T-type calcium channels cause bursts of spikes in motor but not sensory thalamic neurons during mimicry of natural patterns of synaptic input

Kim, Haram R.,Hong, Su Z.,Fiorillo, Christopher D. Frontiers Media S.A. 2015 Frontiers in cellular neuroscience Vol.9 No.-

<P>Although neurons within intact nervous systems can be classified as ‘sensory’ or ‘motor,’ it is not known whether there is any general distinction between sensory and motor neurons at the cellular or molecular levels. Here, we extend and test a theory according to which activation of certain subtypes of voltage-gated ion channel (VGC) generate patterns of spikes in neurons of motor systems, whereas VGC are proposed to counteract patterns in sensory neurons. We previously reported experimental evidence for the theory from visual thalamus, where we found that T-type calcium channels (TtCCs) did not cause bursts of spikes but instead served the function of ‘predictive homeostasis’ to maximize the causal and informational link between retinogeniculate excitation and spike output. Here, we have recorded neurons in brain slices from eight sensory and motor regions of rat thalamus while mimicking key features of natural excitatory and inhibitory post-synaptic potentials. As predicted by theory, TtCC did cause bursts of spikes in motor thalamus. TtCC-mediated responses in motor thalamus were activated at more hyperpolarized potentials and caused larger depolarizations with more spikes than in visual and auditory thalamus. Somatosensory thalamus is known to be more closely connected to motor regions relative to auditory and visual thalamus, and likewise the strength of its TtCC responses was intermediate between these regions and motor thalamus. We also observed lower input resistance, as well as limited evidence of stronger hyperpolarization-induced (‘H-type’) depolarization, in nuclei closer to motor output. These findings support our theory of a specific difference between sensory and motor neurons at the cellular level.</P>

The oldest modern lizard trackways from the Early Cretaceous Hasandong Formation in Hadong County, Korea

Yuong-Nam Lee,Hang-Jae Lee,Anthony R. Fiorillo,Junchang Lu 대한지질학회 2017 대한지질학회 학술대회 Vol.2017 No.10

Unusual locomotion behaviour preserved within a crocodyliform trackway from the Upper Cretaceous Bayanshiree Formation of Mongolia and its palaeobiological implications

Lee, Yuong-Nam,Lee, Hang-Jae,Kobayashi, Yoshitsugu,Paulina-Carabajal, Ariana,Barsbold, Rinchen,Fiorillo, Anthony R.,Tsogtbaatar, Khishigjav Elsevier 2019 Palaeogeography, palaeoclimatology, palaeoecology Vol.533 No.-

<P><B>Abstract</B></P> <P>Crocodyliform tracks are reported from the Upper Cretaceous (?Cenomanian-Santonian) Bayanshiree Formation in southeastern Mongolia. Ten tracks are preserved as natural casts, forming a trackway with a quadrupedal gait pattern with a tail trail. All tracks are short and wide, and dominated by toe traces without plantar impressions. Pes tracks are characterized by four deep claw impressions and push-back marks behind them. Manus tracks have shallow claw marks and long, sub-parallel scratch marks behind. The preferential association of the scratch marks with only the distal digit impressions and irregular pattern of footfalls suggests that this trackway was made by a bottom walking and punting crocodyliform under water. This trackway represents the first crocodyliform “swim tracks” in the Late Cretaceous of Asia and the first evidence for punting behaviour of a fossil crocodyliform. The “swim tracks” can be divided into two categories such as bottom walking tracks with punting for moving somewhat more quickly and subaqueous walking tracks without punting to be associated with slower underwater speeds. The tracks show that crocodylians had adopted a bottom walking behaviour similar to extant crocodylians by Cretaceous times.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The first report of crocodyliform “swim tracks” in the Late Cretaceous of Asia </LI> <LI> The first evidence for punting behaviour of a fossil crocodyliform </LI> <LI> Conspicuous dragging behaviour during bottom walking </LI> <LI> Division into two categories of crocodyliform “swim tracks” </LI> </UL> </P>