Critical roles of mecamylamine-sensitive mushroom body neurons in insect olfactory learning

In insects, cholinergic neurons are thought to transmit olfactory conditioned stimulus (CS) to the sites for associating the CS with unconditioned stimulus (US), but the types of acetylcholine (ACh) receptor used by neurons participating in the association have not been determined. In cockroaches, a type of nicotinic ACh receptor specifically antagonized by mecamylamine (MEC) has been characterized. Here we investigated the roles of neurons possessing MEC-sensitive ACh receptors (MEC-sensitive neurons) in olfactory conditioning of salivation, monitored by changes in activities of salivary neurons, in cockroaches. Local and bilateral microinjection of MEC into each of the three olfactory centers, antennal lobes, calyces of the mushroom bodies and lateral protocerebra, impaired olfactory responses of salivary neurons, indicating that MEC-sensitive neurons in all olfactory centers participate in pathways mediating olfactory responses of salivary neurons. Conditioning of olfactory CS with sucrose US was impaired by injection of MEC into the antennal lobes or calyces, i.e., conditioned responses were absent even after recovery from MEC injection, suggesting that the CS-US association occurs in MEC-sensitive neurons in calyces (most probably Kenyon cells) or in neurons in downstream pathways. In contrast, conditioned responses appeared after recovery from MEC injection into the lateral protocerebra, suggesting that MEC-sensitive neurons in the lateral protocerebra are downstream of the association sites. Since lateral protocerebra are major termination areas of mushroom body efferent neurons, we suggest that input synapses of MEC-sensitive Kenyon cells, or their output synapses upon mushroom body efferent neurons, are the sites for CS-US association for conditioning of salivation.     

Do birds (pigeons and bantams) know how confident they are of their perceptual decisions?

Rhesus monkeys are known to recognize confidence about their immediate perceptual and cognitive decisions by using a betting procedure (Son and Kornell in The missing link in cognition: origins of self-reflective consciousness. Oxford University Press, New York, pp 296–320, 2005; Kornell et al. in Psychol Sci 18:64–71, 2007). In this report, we examined whether this ability is shared in two avian species (pigeons and bantams) in order to know how widespread this metacognitive ability is among animals. We trained pigeons and bantams to search for a differently colored disk (target) among others (distracters) displayed on a touch-sensitive monitor. In test, the subjects were required to choose one of two confidence icons, “risk” and “safe”, after the visual search. A peck at the “risk” icon after a correct response in the visual search (i.e., a peck at the target) was reinforced by food and light, while that after an incorrect response (i.e., a peck at a distracter) resulted in a timeout. A peck at the “safe” icon was always reinforced by food and light, or by light only, regardless of the visual search result. The percentages of “safe” choices after incorrect responses were higher than after correct responses in all six pigeons and two of three bantams. This behavior generalized to novel stimuli in some subjects, and even to a novel line-classification task in a pigeon. These results suggest that these two distantly related avian species have in common a metacognitive ability that allows them to recognize confidence about their immediate perceptual decisions.     

Initial-state dependency of learning in young infants

With the aim of investigating the effect of the initial state of pre-learning on subsequent infant learning (i.e., the initial-state dependency), we observed the limb movements in 3-month-old infants in the course of a motor learning task. The session comprised 2-min pre-learning and 4-min learning periods, and the infants learned to move a toy using a string attached to either an arm (arm-based learning, Experiment 1) or a leg (leg-based learning, Experiment 2). Infants were assigned to low- and high-state groups in the initial-state condition according to the average velocity of the arm (Experiment 1) or leg (Experiment 2) movements during the pre-learning period. The results revealed that, during the learning period, infants in the low-state group increased the movement of their limbs, whereas those in the high-state group showed no significant changes in the movement of most of their limbs. These results suggest that infants demonstrating a low average velocity of movement in the initial state easily observed and learned the circular causality between self-produced movements and environmental changes. On the other hand, it seemed that infants demonstrating a high average velocity of movement in the initial state could not or did not need to increase their limb movements (the toy would already be shaking enough to form striking movements).     

Pigeons perceive a reversed Zöllner illusion

Pigeons are susceptible to several size and length illusions, but in some cases the bias has been shown to be opposite to that seen in humans. To further investigate how their perceptual system works, we asked how pigeons perceive orientation illusions. We used the Zöllner illusion, in which parallel lines look non-parallel due to series of short crosshatches superimposed on the lines. First, we trained six birds to peck at the narrower (or wider) of the two gaps at the end of a pair of non-parallel target lines. After adapting the subjects to target lines with randomly oriented crosshatches (which result in no illusion at least to humans), we tested the pigeons’ responses on randomly inserted probe trials, in which crosshatches that should induce the standard Zöllner-like illusion for humans replaced the random-oriented ones. The results suggested that pigeons do perceive an illusion from Zöllner figures, but in the direction opposite to that of humans. We propose that pigeons, contrary to humans, may assimilate the two lines of different orientations (each main line and crosshatch), which results in underestimation of acute angles, and this in turn may lead to a reversed Zöllner illusion. Such assimilation dominance appears consistent with previous reports obtained for line length and size illusions in this species.     

Large-billed crows (Corvus macrorhynchos) have retrospective but not prospective metamemory

Evidence of metamemory, the ability to monitor one’s own memory, has been obtained in some primates, but it appears to be weaker in other species. In this study, we examined whether crows flexibly modulate their behavior by monitoring the strength of memory trace in a delayed matching-to-sample task using two paradigms. First, crows performing a memory test were given an escape option to decline taking the test (prospective metamemory). Second, crows were given the escape option as a “not confident” report after completing the test (retrospective metamemory). Accurate memory performance yielded a reward with a higher probability, whereas inaccurate memory performance resulted in no such recompense. The escape option yielded a reward with a lower probability. In the prospective metamemory test, crows escaped the memory test more frequently with longer delay intervals than they did with shorter delay intervals but no more frequently in the sample-omission than the sample-present trials, indicating that the crows decided to take the test or decline it by using the delay interval as a cue. In contrast, in the retrospective metamemory test, the crows escaped the memory test more frequently when their memory-test response was incorrect than correct and more frequently in the sample-omission than the sample-present trials, indicating that the crows recognized confidence regarding their choice in the memory test and utilized the escape option to maximize reward probability. Although these results suggest that crows retrospectively monitor the strength of memory trace, their prospective metamemory ability has not yet been confirmed in the present paradigm.     

Deliberate Self‐Harm in Adolescents Aged 12–18: A Cross‐Sectional Survey of 18,104 Students

Little is known about accurate prevalence and associated factors of deliberate self‐harm (DSH) among adolescents in Asian countries. In this study, the prevalence and associated factors of DSH among adolescents in Japan were examined. Data were derived from a cross‐sectional survey using an anonymous self‐report questionnaire and enrolling 8,620 adolescents aged 12–15 and 9,484 aged 15–18. DSH in the previous 12 months was reported by 3.3% (95% CI, 2.9–3.7) of junior and 4.3% (3.9%–4.7%) of senior high school respondents. The prevalence was more than four times as high among girls as among boys for both age groups. DSH was further strongly associated with having suicidal thoughts, having depression/anxiety symptoms, and having used recreational drugs. These associated factors were similar for both sexes and for both older and younger teenagers. A substantial minority of adolescents present with DSH, even among those aged 12–15. The prevalence of DSH in Japan was in the lower ranges of those reported for Western countries. The identified associated factors were not dissimilar from those reported in the West.     

Attentional modulation in perception of visual motion events.

Identical visual targets moving across each other with equal and constant speed can be perceived either to bounce off or to stream through each other. This bistable motion perception has been studied mostly in the context of motion integration. Since the perception of most ambiguous motion is affected by attention, there is the possibility of attentional modulation occurring in this case as well. We investigated whether distraction of attention from the moving targets would alter the relative frequency of each percept. During the observation of the streaming/bouncing motion event in the peripheral visual field, visual attention was disrupted by an abrupt presentation of a visual distractor at various timings and locations (experiment 1; exogenous distraction of attention) or by the demand of an additional discrimination task (experiments 2 and 3; endogenous distraction of attention). Both types of distractions of attention increased the frequency of the bouncing percept and decreased that of the streaming percept. These results suggest that attention may facilitate the perception of object motion as continuing in the same direction as in the past.