Research Interests: Theoretical Neuroscience
Overview: Our lab is focused on elucidating the neural basis of sensory perception, decision-making, and associative learning.
- How does behavior emerge from the complex temporal interactions of cortical and subcortical networks?
- How do different physiological states, such as arousal, disengagement, expectation, affect sensory processing and modulate an animal's behavior?
- What drives associative learning at the level of synaptic plasticity in cortical and subcortical circuits?
To study these and other questions, we use methods from statistical physics, information theory, machine learning, and dynamical systems. We combine analysis of neurophysiological data from large populations of neurons in behaving animals with theoretical models based on neural networks.
Our lab is passionate about creating an inclusive environment promoting diversity. We embrace a notion of intellectual community enhanced by diversity along a number of dimensions, including race, ethnicity and national origins, gender identity and presentation, disability, class and religion. We aim at fostering greater creativity and encouraging collaborative innovation and interactions.
Stimuli Reduce the Dimensionality of Cortical Activity.
Front Syst Neurosci. 2016;10:11
Authors: Mazzucato L, Fontanini A, La Camera G
The activity of ensembles of simultaneously recorded neurons can be represented as a set of points in the space of firing rates. Even though the dimension of this space is equal to the ensemble size, neural activity can be effectively localized on smaller subspaces. The dimensionality of the neural space is an important determinant of the computational tasks supported by the neural activity. Here, we investigate the dimensionality of neural ensembles from the sensory cortex of alert rats during periods of ongoing (inter-trial) and stimulus-evoked activity. We find that dimensionality grows linearly with ensemble size, and grows significantly faster during ongoing activity compared to evoked activity. We explain these results using a spiking network model based on a clustered architecture. The model captures the difference in growth rate between ongoing and evoked activity and predicts a characteristic scaling with ensemble size that could be tested in high-density multi-electrode recordings. Moreover, we present a simple theory that predicts the existence of an upper bound on dimensionality. This upper bound is inversely proportional to the amount of pair-wise correlations and, compared to a homogeneous network without clusters, it is larger by a factor equal to the number of clusters. The empirical estimation of such bounds depends on the number and duration of trials and is well predicted by the theory. Together, these results provide a framework to analyze neural dimensionality in alert animals, its behavior under stimulus presentation, and its theoretical dependence on ensemble size, number of clusters, and correlations in spiking network models.
PMID: 26924968 [PubMed]
Dynamics of multistable states during ongoing and evoked cortical activity.
J Neurosci. 2015 May 27;35(21):8214-31
Authors: Mazzucato L, Fontanini A, La Camera G
Single-trial analyses of ensemble activity in alert animals demonstrate that cortical circuits dynamics evolve through temporal sequences of metastable states. Metastability has been studied for its potential role in sensory coding, memory, and decision-making. Yet, very little is known about the network mechanisms responsible for its genesis. It is often assumed that the onset of state sequences is triggered by an external stimulus. Here we show that state sequences can be observed also in the absence of overt sensory stimulation. Analysis of multielectrode recordings from the gustatory cortex of alert rats revealed ongoing sequences of states, where single neurons spontaneously attain several firing rates across different states. This single-neuron multistability represents a challenge to existing spiking network models, where typically each neuron is at most bistable. We present a recurrent spiking network model that accounts for both the spontaneous generation of state sequences and the multistability in single-neuron firing rates. Each state results from the activation of neural clusters with potentiated intracluster connections, with the firing rate in each cluster depending on the number of active clusters. Simulations show that the model's ensemble activity hops among the different states, reproducing the ongoing dynamics observed in the data. When probed with external stimuli, the model predicts the quenching of single-neuron multistability into bistability and the reduction of trial-by-trial variability. Both predictions were confirmed in the data. Together, these results provide a theoretical framework that captures both ongoing and evoked network dynamics in a single mechanistic model.
PMID: 26019337 [PubMed - indexed for MEDLINE]
Processing of hedonic and chemosensory features of taste in medial prefrontal and insular networks.
J Neurosci. 2013 Nov 27;33(48):18966-78
Authors: Jezzini A, Mazzucato L, La Camera G, Fontanini A
Most of the research on cortical processing of taste has focused on either the primary gustatory cortex (GC) or the orbitofrontal cortex (OFC). However, these are not the only areas involved in taste processing. Gustatory information can also reach another frontal region, the medial prefrontal cortex (mPFC), via direct projections from GC. mPFC has been studied extensively in relation to its role in controlling goal-directed action and reward-guided behaviors, yet very little is known about its involvement in taste coding. The experiments presented here address this important point and test whether neurons in mPFC can significantly process the physiochemical and hedonic dimensions of taste. Spiking responses to intraorally delivered tastants were recorded from rats implanted with bundles of electrodes in mPFC and GC. Analysis of single-neuron and ensemble activity revealed similarities and differences between the two areas. Neurons in mPFC can encode the chemosensory identity of gustatory stimuli. However, responses in mPFC are sparser, more narrowly tuned, and have a later onset than in GC. Although taste quality is more robustly represented in GC, taste palatability is coded equally well in the two areas. Additional analysis of responses in neurons processing the hedonic value of taste revealed differences between the two areas in temporal dynamics and sensitivities to palatability. These results add mPFC to the network of areas involved in processing gustatory stimuli and demonstrate significant differences in taste-coding between GC and mPFC.
PMID: 24285901 [PubMed - indexed for MEDLINE]
Lack of evidence for monosomy 1p36 in patients with Prader-Willi-like phenotype.
Braz J Med Biol Res. 2008 Aug;41(8):681-3
Authors: Rodríguez VR, Mazzucato LF, Pina-Neto JM
Monosomy 1p36 is the most common subtelomeric microdeletion syndrome with an incidence rate estimated to be 1 in 5000 births. A hypothesis of a similarity between patients with 1p36 deletion and those with Prader-Willi syndrome and the existence of two different phenotypes for 1p36 microdeletion has been suggested. The main objective of the present study was to determine the existence of 1p36 microdeletion in a sample of patients with mental retardation, obesity and hyperphagia who tested negative by the methylation test for Prader-Willi syndrome. Sixteen patients (7 females, 9 males), 16-26 years old, were evaluated with high-resolution cytogenetic analysis at 550-850 band levels and with 11 polymorphic microsatellite markers located in the 1p36 region. All patients had normal cytogenetic and molecular results. The results obtained by high-resolution cytogenetic methodology were confirmed by the molecular analyses. We did not detect a 1p36 microdeletion in 16 subjects with the Prader-Willi-like phenotype, which reinforces that no correlation seems to exist between Prader-Willi-like phenotype and the 1p36 microdeletion syndrome.
PMID: 18797701 [PubMed - indexed for MEDLINE]
Reconstruction of the health status in a past human population: the Iron Age necropolis of Monte Bibele (Bologna, Italy).
Anthropol Anz. 1997 Dec;55(3-4):247-64
Authors: Brasili P, Facchini F, Scarani P, Mazzucato L
This paper examines the condition of health of an iron age population from Monte Bibele (Bologna, Italy). The vertebral spine is the site most frequently affected by disease: cleft atlas, spina bifida of the sacrum, sacralization of the 5th lumbar spine, arthrosis. Arthrosis is also present in the hip, elbow, shoulder and knee. Fractures are common. Periostitis and osteoporosis and a probable case of acromegaly are present. The majority of the pathologic changes observed in the population of Monte Bibele appears to be related to senescence or to occupational causes.
PMID: 9468754 [PubMed - indexed for MEDLINE]
[Evaluation of dietary sodium intake in epidemiological studies: methods and problems].
G Ital Cardiol. 1990 Dec;20(12):1155-60
Authors: Zamboni S, Urbani V, Mazzucato L, Ambrosio GB, Semplicini A, Dal Palů C
PMID: 2083813 [PubMed - indexed for MEDLINE]
[Erythrocyte Li/Na countertransport and correlated variables in a randomized sample of population].
Cardiologia. 1989 Apr;34(4):347-51
Authors: Mozzato MG, Semplicini A, Zamboni S, Urbani V, Marzola M, Mazzucato L, Ambrosio GB, Pessina AC
A genetically determined alteration of the cell membrane sodium metabolism may play a role in the pathogenesis of essential hypertension. The most consistent finding in patients with essential hypertension is an increased red blood cell Li/Na exchange (countertransport). It is genetically determined but it is also associated to potentially confounding variables (body weight, race, age and so on). The present study investigates the relationship between red cell Li/Na countertransport and various potentially confounding variables in a random sample of the population. It shows that this membrane cation transport system is increased in males compared to females and significantly correlated to body mass index in males and to blood pressure, alcohol consumption and, negatively, to urinary calcium excretion in females. Since body weight and alcohol consumption are correlated to blood pressure in several epidemiological studies, it can be hypothesized that they influence blood pressure control through an alteration of the cell membrane sodium transport.
PMID: 2758440 [PubMed - indexed for MEDLINE]
Electrocardiographic findings in hypertensive patients of a population sample. Role of sex, age, and antihypertensive treatment.
J Clin Hypertens. 1987 Dec;3(4):430-8
Authors: Zamboni S, Ambrosio GB, Stefanini MG, Urbani V, Dissegna L, Mazzucato L, Zahalka T, Dal Palù C
During the initial phase of the World Health Organization (WHO) "Community Control Program of Hypertension" in Italy, 1190 subjects with high blood pressure derived from a general population random sample (5856 people of both sexes, aged 20 to 64 years) were enrolled in a hypertension register. At the registration visit (RV), each of them gave case history details and underwent a complete clinical examination, blood and urine tests, and a standard 12-lead electrocardiogram (ECG). All the ECGs were read by a single coder, using the second version of the Minnesota Code (MC). We calculated the prevalence of electrocardiographic codes according to sex, age, and the state of antihypertensive treatment. The overall prevalence of electrocardiographic abnormalities (i.e., all codes except 1:0 and isolated 9:4) was 40.8% with a slightly higher prevalence in males than in females: 42.4% versus 39.4%. Codes related to left ventricular hypertrophy (LVH) (3:1 or 3:3) were also more frequent in males (21.2%) than in females (14.5%) but not those related to ischemia (4:1-4:3 or 5:1-5:3). In fact, group 4 codes were present in 4.0% of males and 16.1% of females; group 5 codes, in 5.7% of males and 18.1% of females. Abnormal codes generally increased with increasing age, but those related to LVH did not follow this general rule in males. In fact, in the age class 20-29 years, codes 3:1 were found in 11.1% and codes 3:3 in 17.5% of the subjects, whereas the corresponding frequencies in the oldest age group (60-64 years) were 15.2% and 12.4%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
PMID: 2969037 [PubMed - indexed for MEDLINE]